diff --git a/src/test/java/teammates/sqlui/webapi/DeleteInstructorActionTest.java b/src/test/java/teammates/sqlui/webapi/DeleteInstructorActionTest.java
new file mode 100644
index 00000000000..6328807e650
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+++ b/src/test/java/teammates/sqlui/webapi/DeleteInstructorActionTest.java
@@ -0,0 +1,296 @@
+package teammates.sqlui.webapi;
+
+import static org.mockito.Mockito.times;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.when;
+
+import java.util.List;
+
+import org.mockito.Mockito;
+import org.testng.annotations.BeforeMethod;
+import org.testng.annotations.Test;
+
+import teammates.common.datatransfer.InstructorPrivileges;
+import teammates.common.util.Const;
+import teammates.storage.sqlentity.Account;
+import teammates.storage.sqlentity.Course;
+import teammates.storage.sqlentity.Instructor;
+import teammates.ui.output.MessageOutput;
+import teammates.ui.webapi.DeleteInstructorAction;
+import teammates.ui.webapi.InvalidOperationException;
+
+/**
+ * SUT: {@link DeleteInstructorAction}.
+ */
+public class DeleteInstructorActionTest extends BaseActionTest<DeleteInstructorAction> {
+
+    private Course course;
+    private Instructor instructor;
+    private Instructor instructor2;
+
+    @Override
+    protected String getActionUri() {
+        return Const.ResourceURIs.INSTRUCTOR;
+    }
+
+    @Override
+    protected String getRequestMethod() {
+        return DELETE;
+    }
+
+    @BeforeMethod
+    void setUp() {
+        Mockito.reset(mockLogic);
+
+        course = new Course("course-id", "Course Name", Const.DEFAULT_TIME_ZONE, "institute");
+        instructor = setupInstructor("instructor-googleId", "name", "instructoremail@tm.tmt");
+        instructor2 = setupInstructor("instructor2-googleId", "name2", "instructor2email@tm.tmt");
+
+        setupMockLogic();
+    }
+
+    private Instructor setupInstructor(String googleId, String name, String email) {
+        Account account = new Account(googleId, name, email);
+        InstructorPrivileges instructorPrivileges = new InstructorPrivileges();
+        instructorPrivileges.updatePrivilege(Const.InstructorPermissions.CAN_MODIFY_INSTRUCTOR, true);
+
+        Instructor instructor = new Instructor(course, name, email,
+                true, "", null, instructorPrivileges);
+        instructor.setAccount(account);
+        return instructor;
+    }
+
+    private void setupMockLogic() {
+        when(mockLogic.getCourse(course.getId())).thenReturn(course);
+        when(mockLogic.getInstructorByGoogleId(course.getId(), instructor.getGoogleId())).thenReturn(instructor);
+        when(mockLogic.getInstructorByGoogleId(course.getId(), instructor2.getGoogleId())).thenReturn(instructor2);
+        when(mockLogic.getInstructorForEmail(course.getId(), instructor.getEmail())).thenReturn(instructor);
+        when(mockLogic.getInstructorForEmail(course.getId(), instructor2.getEmail())).thenReturn(instructor2);
+        when(mockLogic.getInstructorsByCourse(course.getId())).thenReturn(List.of(instructor, instructor2));
+    }
+
+    @Test
+    void testExecute_deleteInstructorByGoogleId_success() {
+        String[] params = {
+                Const.ParamsNames.COURSE_ID, course.getId(),
+                Const.ParamsNames.INSTRUCTOR_ID, instructor2.getGoogleId(),
+        };
+
+        DeleteInstructorAction action = getAction(params);
+        MessageOutput actionOutput = (MessageOutput) getJsonResult(action).getOutput();
+
+        verify(mockLogic, times(1)).deleteInstructorCascade(course.getId(), instructor2.getEmail());
+        assertEquals("Instructor is successfully deleted.", actionOutput.getMessage());
+    }
+
+    @Test
+    void testExecute_deleteInstructorByEmail_success() {
+        String[] params = {
+                Const.ParamsNames.COURSE_ID, course.getId(),
+                Const.ParamsNames.INSTRUCTOR_EMAIL, instructor2.getEmail(),
+        };
+
+        DeleteInstructorAction action = getAction(params);
+        MessageOutput actionOutput = (MessageOutput) getJsonResult(action).getOutput();
+
+        verify(mockLogic, times(1)).deleteInstructorCascade(course.getId(), instructor2.getEmail());
+        assertEquals("Instructor is successfully deleted.", actionOutput.getMessage());
+    }
+
+    @Test
+    void testExecute_deleteLastInstructorByGoogleId_fail() {
+        // Override the mock logic for the course to have only one instructor
+        when(mockLogic.getInstructorsByCourse(course.getId())).thenReturn(List.of(instructor));
+
+        String[] params = {
+                Const.ParamsNames.COURSE_ID, course.getId(),
+                Const.ParamsNames.INSTRUCTOR_ID, instructor.getGoogleId(),
+        };
+
+        assertEquals(mockLogic.getInstructorsByCourse(course.getId()).size(), 1);
+
+        InvalidOperationException ioe = verifyInvalidOperation(params);
+        assertEquals("The instructor you are trying to delete is the last instructor in the course. "
+                + "Deleting the last instructor from the course is not allowed.", ioe.getMessage());
+
+        verify(mockLogic, times(0)).deleteInstructorCascade(course.getId(), instructor.getEmail());
+    }
+
+    @Test
+    void testExecute_instructorDeleteOwnRoleByGoogleId_success() {
+        loginAsInstructor(instructor.getGoogleId());
+
+        String[] params = {
+                Const.ParamsNames.COURSE_ID, course.getId(),
+                Const.ParamsNames.INSTRUCTOR_ID, instructor.getGoogleId(),
+        };
+
+        DeleteInstructorAction action = getAction(params);
+        MessageOutput actionOutput = (MessageOutput) getJsonResult(action).getOutput();
+
+        verify(mockLogic, times(1)).deleteInstructorCascade(course.getId(), instructor.getEmail());
+        assertEquals("Instructor is successfully deleted.", actionOutput.getMessage());
+    }
+
+    @Test
+    void testExecute_deleteNonExistentInstructorByGoogleId_failSilently() {
+        when(mockLogic.getInstructorByGoogleId(course.getId(), "fake-googleId")).thenReturn(null);
+
+        String[] params = {
+                Const.ParamsNames.COURSE_ID, course.getId(),
+                Const.ParamsNames.INSTRUCTOR_ID, "fake-googleId",
+        };
+
+        assertNull(mockLogic.getInstructorByGoogleId(course.getId(), "fake-googleId"));
+
+        DeleteInstructorAction action = getAction(params);
+        MessageOutput actionOutput = (MessageOutput) getJsonResult(action).getOutput();
+
+        verify(mockLogic, times(0)).deleteInstructorCascade(course.getId(), instructor.getEmail());
+        assertEquals("Instructor is successfully deleted.", actionOutput.getMessage());
+    }
+
+    @Test
+    void testExecute_deleteNonExistentInstructorByEmail_failSilently() {
+        String fakeInstructorEmail = "fake-instructoremail@tm.tmt";
+        when(mockLogic.getInstructorForEmail(course.getId(), fakeInstructorEmail)).thenReturn(null);
+
+        String[] params = {
+                Const.ParamsNames.COURSE_ID, course.getId(),
+                Const.ParamsNames.INSTRUCTOR_EMAIL, fakeInstructorEmail,
+        };
+
+        assertNull(mockLogic.getInstructorForEmail(course.getId(), fakeInstructorEmail));
+
+        DeleteInstructorAction action = getAction(params);
+        MessageOutput actionOutput = (MessageOutput) getJsonResult(action).getOutput();
+
+        verify(mockLogic, times(0)).deleteInstructorCascade(course.getId(), fakeInstructorEmail);
+        assertEquals("Instructor is successfully deleted.", actionOutput.getMessage());
+    }
+
+    @Test
+    void testExecute_courseDoesNotExist_failSilently() {
+        String nonExistentCourseId = "non-existent-course-id";
+        when(mockLogic.getCourse(nonExistentCourseId)).thenReturn(null);
+
+        String[] params = {
+                Const.ParamsNames.COURSE_ID, nonExistentCourseId,
+                Const.ParamsNames.INSTRUCTOR_ID, instructor.getGoogleId(),
+        };
+
+        DeleteInstructorAction action = getAction(params);
+        MessageOutput actionOutput = (MessageOutput) getJsonResult(action).getOutput();
+
+        verify(mockLogic, times(0)).deleteInstructorCascade(nonExistentCourseId, instructor.getEmail());
+        assertEquals("Instructor is successfully deleted.", actionOutput.getMessage());
+    }
+
+    @Test
+    void testExecute_noParameters_throwsInvalidHttpParameterException() {
+        verifyHttpParameterFailure();
+    }
+
+    @Test
+    void testExecute_missingCourseIdWithInstructorId_throwsInvalidHttpParameterException() {
+        String[] params = {
+                Const.ParamsNames.INSTRUCTOR_ID, instructor.getGoogleId(),
+        };
+
+        verifyHttpParameterFailure(params);
+    }
+
+    @Test
+    void testExecute_missingCourseIdWithInstructorEmail_throwsInvalidHttpParameterException() {
+        String[] params = {
+                Const.ParamsNames.INSTRUCTOR_EMAIL, instructor.getEmail(),
+        };
+
+        verifyHttpParameterFailure(params);
+    }
+
+    @Test
+    void testExecute_onlyCourseId_throwsInvalidHttpParameterException() {
+        String[] params = {
+                Const.ParamsNames.COURSE_ID, course.getId(),
+        };
+
+        verifyHttpParameterFailure(params);
+    }
+
+    @Test
+    void testSpecificAccessControl_admin_canAccess() {
+        loginAsAdmin();
+
+        String[] params = {
+                Const.ParamsNames.COURSE_ID, course.getId(),
+                Const.ParamsNames.INSTRUCTOR_ID, instructor.getGoogleId(),
+        };
+
+        verifyCanAccess(params);
+    }
+
+    @Test
+    void testSpecificAccessControl_instructorWithPermission_canAccess() {
+        loginAsInstructor(instructor.getGoogleId());
+
+        String[] params = {
+                Const.ParamsNames.COURSE_ID, course.getId(),
+                Const.ParamsNames.INSTRUCTOR_ID, instructor2.getGoogleId(),
+        };
+
+        verifyCanAccess(params);
+    }
+
+    @Test
+    void testSpecificAccessControl_instructorWithInvalidPermission_cannotAccess() {
+        InstructorPrivileges instructorPrivileges = new InstructorPrivileges();
+        instructorPrivileges.updatePrivilege(Const.InstructorPermissions.CAN_MODIFY_INSTRUCTOR, false);
+        instructor.setPrivileges(instructorPrivileges);
+
+        loginAsInstructor(instructor.getGoogleId());
+
+        String[] params = {
+                Const.ParamsNames.COURSE_ID, course.getId(),
+                Const.ParamsNames.INSTRUCTOR_ID, instructor2.getGoogleId(),
+        };
+
+        verifyCannotAccess(params);
+    }
+
+    @Test
+    void testSpecificAccessControl_instructorInDifferentCourse_cannotAccess() {
+        loginAsInstructor("instructor3-googleId");
+
+        String[] params = {
+                Const.ParamsNames.COURSE_ID, course.getId(),
+                Const.ParamsNames.INSTRUCTOR_ID, instructor.getGoogleId(),
+        };
+
+        verifyCannotAccess(params);
+    }
+
+    @Test
+    void testSpecificAccessControl_student_cannotAccess() {
+        loginAsStudent("student-googleId");
+
+        String[] params = {
+                Const.ParamsNames.COURSE_ID, course.getId(),
+                Const.ParamsNames.INSTRUCTOR_ID, instructor.getGoogleId(),
+        };
+
+        verifyCannotAccess(params);
+    }
+
+    @Test
+    void testSpecificAccessControl_loggedOut_cannotAccess() {
+        logoutUser();
+
+        String[] params = {
+                Const.ParamsNames.COURSE_ID, course.getId(),
+                Const.ParamsNames.INSTRUCTOR_ID, instructor.getGoogleId(),
+        };
+
+        verifyCannotAccess(params);
+    }
+}