The 1988–89 season was Sport Lisboa e Benfica's 85th season in existence and the club's 55th consecutive season in the top flight of Portuguese football, covering the period from 1 July 1988 to 30 June 1989. Benfica competed domestically in the Primeira Divisão and the Taça de Portugal, and participated in the UEFA Cup after finishing second in the previous league.

After leading Benfica to their sixth European Cup Final, Toni remained in charge of the team. He lost Rui Águas and Dito to Porto in a controversial case known as "Ademir affair"; but new signings such as Valdo Filho, Vata, Ricardo Gomes, and Ademir Alcântara helped guide the team to the 28th league title. Despite several draws in the first half of the season, and two losses between both half's, Benfica was much more regular. Several consecutive wins opened a six-point lead over Porto, with the title arriving on 7 May. Benfica also contested the 1989 Taça de Portugal Final, but lost it to Belenenses.

For the new season former assistant manager, Toni remained in charge of the team after leading them to the European Cup Final. The off-season was marked by tension between Porto and Benfica, after the first signed Rui Águas and Dito, breaking a 20-year gentlemen's agreement of not signing each other's players. The dispute boiled down to the signing of Ademir Alcântara, with Porto accusing Benfica of stealing the player. It became known as the "Ademir affair". To replace Águas and Dito, Benfica signed Vata and Ricardo Gomes, and added Brazilian international Valdo Filho, amidst several others, including the aforementioned Ademir. The pre-season began on 18 July, with medical tests. The next day, Benfica travelled to Lamego for eleven days of training sessions. Afterwards, they embarked on a tour to the Netherlands, where they competed in the Amsterdam Tournament from 5 to 7 August. Their presentation game occurred on the 11 with Grêmio, and they closed the pre-season with a second tournament, the Marlboro Cup in New York. This caused the opening game with Penafiel, scheduled for 21 August to be postponed to 14 September.

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