Sakho began his career in the lower divisions of French football, with Metz and on loan at Boulogne, before joining West Ham United in August 2014.

[4] He started his career in Dakar with Génération Foot, a football academy and feeder club for FC Metz, at age 16.

In May 2012, with Metz in Championnat National, the third tier of French football, new manager Albert Cartier gave Sakho a starting place in the team.

The following season Sakho scored 19 goals in 33 league appearances as Metz finished in second place and won promotion back to Ligue 2 at their first attempt.

[6] Sakho made his West Ham debut on 23 August 2014, in a 3–1 away win against Crystal Palace, coming on as a 63rd-minute substitute for Carlton Cole.

[10] He made his home debut against Liverpool on 20 September, and scored his second goal with a chip over goalkeeper Simon Mignolet as the Hammers won 3–1.

[12] On 25 October 2014 Sakho scored West Ham's second goal in a 2–1 home win against reigning champions, Manchester City.

Unable to fly to Africa he was taken from London to Ashton Gate by limousine and on 25 January 2015 he scored the only goal in West Ham's FA Cup win against Bristol City.

[23] Sakho opened the 2015–16 season by scoring the first two goals in a UEFA Europa League first qualifying round first-leg game on 2 July, as West Ham won 3–0 at home against Andorran team Lusitanos.

[24] In the return leg a week later, he was sent-off for violent conduct in the 15th minute after "raising his hands" to Lusitanos player Moisés San Nicolás.

[29] In August 2016, a proposed transfer to West Bromwich Albion collapsed after Sakho failed a medical.

[37] On 31 August 2018, the last day of the 2018 summer transfer window, Sakho joined Süper Lig side Bursaspor on loan for the season.

[38] On 19 June 2020, Sakho joined Swiss Super League side Neuchâtel Xamax on a deal until the end of the season.

[6] In November 2014 he was recalled to the Senegal squad by coach, Alain Giresse, for the 2015 Africa Cup of Nations qualification games against Egypt and Botswana.

[46] Sakho was arrested on 6 August 2015 on suspicion of common assault, criminal damage and malicious communication towards his girlfriend.