The 1990 Big West Conference men's basketball tournament was held March 7–10 at the Long Beach Arena in Long Beach, California.
[1] Defending champions UNLV defeated fourth-seeded Long Beach State in the final, 92–72, and captured their sixth PCAA/Big West championship.
UNLV, in turn, received an automatic bid to the 1990 NCAA tournament, which they would go on to win.
Fellow Big West members New Mexico State and UC Santa Barbara received at-large bids.
All ten conference members participated in the field, with teams seeded in the bracket based on regular season conference records.