Bruno was hired in June, signing a two-year deal to replace Sergio Conceicao who had left the club after seven seasons in which he won 11 titles, including three Portuguese league championships.
Porto are the 12th club to change manager this season, which also includes Benfica, who sacked German Roger Schmidt after two campaigns in August, and Sporting who lost Ruben Amorim to Manchester United in November.
Bruno's relationship with the players turned sour after Porto were knocked out the League Cup following a 1-0 loss to Sporting in the semi-final, with midfielder Pepe criticising the coach on social media.
Porto, who are one of the 32 teams to have qualified for the expanded 2025 Club World Cup to be held in the United States from June 15 to July 13, face Olympiacos on Thursday in the Europa League.