Rahman began his career at Dreams FC of the Ghana Division Two. After impressive performances, he was then transferred on loan to Asante Kotoko of the Ghanaian Premier League for one season. For the 2012 season, Rahman was a finalist for the league's Discovery of the Year Award, eventually losing to Joshua Oniku. After becoming a sought after player during his time with the Kumasi-based club, serious enquiries were made about the player by Manchester City and Arsenal of the Premier League and Parma of Serie A.
Germany
However, Rahman eventually signed with newly promoted Greuther Fürth in the Bundesliga on 12 June 2012. Rahman stated that his decision to join Fürth was because the club offered, "the best conditions in which to develop my career." In the derby against 1. FC Nürnberg on 11 August 2014 he scored his first two goals for Fürth in a 5–1 home victory. The next day he signed with FC Augsburg of the same division. In Rahman's 2014–15 season with Augsburg, he made 108 tackles, more than any other player in the Bundesliga that season. Using aspects of his strength and pace, he was able to win 90 of those tackles, coming out to an 83% successful tackle rate. That season, Rahman also had 83 interceptions and won 80 contested aerial balls.
Chelsea
2015–16 season
On 16 August 2015, Rahman signed for Chelsea on a five-year deal for an undisclosed fee, reported to be an initial £14 million, rising to a potential fee of almost £22 million. He made his debut on 16 September in a UEFA Champions League tie, playing the full 90 minutes in a 4–0 win at home to Maccabi Tel Aviv. He made his Premier League debut in a 2–0 win over Aston Villa at Stamford Bridge on 17 October. He played at left-back in games including their 2–1 Champions League win over Dynamo Kyiv. On 27 February, Rahman made an error which allowed Southampton's Shane Long to score in the 42nd minute; he was substituted for Kenedy at half time but Chelsea eventually won 2–1 at St. Mary's.
On 2 August 2016, FC Schalke 04 confirmed that Baba Rahman had moved on a season-long loan to the club after failing to impress the new Chelsea manager Antonio Conte during pre-season. Baba was given the number 14 jersey for the upcoming season. He was signed by his former Augsburg manager, Markus Weinzierl. Rahman told the local newspaper Ruhr Nachrichten that Conte advised him to leave on loan because he preferred more defensive players than him. Rahman made his competitive debut for the Gelsenkirchen team on 20 August, as a winger instead of a defender in a 4–1 victory against FC 08 Villingen in the first round of the DFB-Pokal. He made his league debut on 27 August, coming on for Sead Kolašinac in the 62nd minute of an eventual 1–0 loss at Eintracht Frankfurt on the first day of the season. Rahman scored his first goal for Schalke on 15 September, the game's only in a Europa League victory at OGC Nice. In January 2018, Rahman joined Schalke 04 on loan for a second time agreeing an 18-month stay until summer 2019.
Reims (loan)
In January 2019, he returned early to Chelsea and was immediately loaned to Stade de Reims until the end of the season.
On 2 September 2019, the last day of transfer window, Baba Rahman was again loaned out in a season-long deal, this time to newly promoted La Liga side Mallorca.
Rahman has "Baba" on the back of his jersey, the name of his Chelsea-supporting father. Baba went to the prestigious Al makiss Senior High School in Navrongo for his second cycle education. In May 2016, Baba married his longtime childhood girlfriend, Salma, in their hometown of Tamale in northern Ghana.
