In March 2012 he won the 80th edition of the Cinque Mulini and came third at the Trofeo Alasport. He was runner-up to Edwin Soi at the Giro Media Blenio in April. Longosiwa was second in the 5000 m at the Shanghai Golden Grand Prix and secured a place on the Kenyan Olympic team with a top three finish at the trials. He ran a 5000 m best of 12:49.04 minutes a month before the 2012 London Olympics then went on to win his first ever major medal, taking the bronze medal in the Olympic 5000 m final. After the Olympics he ran in the 2012 Diamond League final, where he placed second behind Isaiah Kiplangat Koech. Two podium finishes at the Giro di Castelbuono and Giro al Sas brought a close to the year for Longosiwa.