[3] Kasubhai began his private legal career in a small civil plaintiff's firm until he opened his own practice, the Law Offices of Mustafa T.

[2] Kasubhai is the first South Asian-American and Muslim judge to be appointed to the Lane County Circuit Court.

[6][7] On June 1, 2023, Kasubhai was one of six names U.S. senators Ron Wyden and Jeff Merkley submitted to the White House for a vacancy on the United States District Court for the District of Oregon created by Marco A. Hernandez, who subsequently assumed senior status on August 21, 2024.

President Biden nominated Kasubhai to the seat being vacated by Judge Ann Aiken, who subsequently assumed senior status on December 29, 2023.

[11] During his confirmation hearing, Republican senators questioned him over a ruling that he made in 2020 regarding the George Floyd protests and his statements and writings about diversity, equity, and inclusion.

[12] Kasubhai was also questioned on guidance he created for the use of preferred pronouns and honorifics in his courtroom, and whether he was a Marxist based on his past writings.

According to Bloomberg Law, "Kasubhai has faced intense opposition from GOP lawmakers who've said that he's too radical for the federal bench.