On December 20, 2018, Ionescu recorded her 13th triple-double in a game against Air Force and broke the NCAA triple-double record for both men and women basketball. She was later named ESPNW Player of the Week. Since that game on December 20, 2018, Ionescu has added five more triple-doubles for a season total of eight, and has broken the Oregon women's basketball assist record (formerly 608 assists) in a Pac-12 conference game against USC. In the 2019 NCAA Tournament, Ionescu leads the Ducks to their first Final Four appearance after their 88–84 victory over Mississippi State. Sabrina finished the game with 31 points, eight assists, seven rebounds and a steal. In the NCAA Tournament Final Four, the Ducks lost to the eventual national champion Baylor 72–67. After the conclusion of the season, Ionescu was named the 2019 John R. Wooden Award winner along with Duke's Zion Williamson. The award is given annually to the most outstanding male and female collegiate basketball player that year. Despite having only played for three seasons at this point, Ionescu was eligible for the 2019 WNBA draft by age. Additionally, she would receive her bachelor's degree that June. However, believing that she had "unfinished business" at Oregon, she chose to come back for her senior season. This announcement came shortly after Ionescu accepted a place in a newly-launched one-year master's degree program in brand creation in UO's School of Journalism and Communications. In the second game of her senior season on November 13, 2019, Ionescu surpassed the 2,000 points, 800 assists mark for her college career with a 109–52 win over Utah State. She fell short of another triple-double with 16 points, 12 assists and 9 rebounds in the game but recorded her 2,012 career points and 810 career assists. In a win over then #3 Stanford (87–55), Ionescu scored a career high 37 points along with 11 rebounds and 7 assists, and broke Alison Lang's Oregon all-time career scoring record of 2,252 points in the third quarter. In the rivalry game against Oregon State on January 24, 2020, Ionescu had 24 points, 9 assists and 4 rebounds and broke Oregon State and NBA star Gary Payton's Pac-12 all-time record of 938 assists. Payton personally congratulated Ionescu on the achievement. On February 14, 2020, Ionescu recorded her 1,000th career assist in a game against #7 UCLA and joined Courtney Vandersloot as the only players in NCAA men's and women's basketball history with 2,000 plus points and 1,000 plus assists.