After a break in competition, Sagan came back in May at the Tour of California. On the first stage, he finished second, in the slipstream of Mark Cavendish. He again came in second position on the next day to Cavendish, but this time he lost by half-a-wheel. On stage 3, Sagan once more reaped second position after a lone breaker, Toms Skujiņš, made it to the finish a minute before him. On Stage 4, Sagan won the day by powering away from Wouter Wippert and Cavendish on the small incline before the line. As he crossed the finish, Sagan banged his front wheel twice on the tarmac and treated the crowd to a no-footed wheelie afterward to celebrate. On the fifth stage, Sagan came in third position. However, in the ensuing Time Trial in Santa Clarita, Sagan imposed himself on the flat and slightly technical circuit, grabbing the general classification jersey in the process. On the following day's seventh stage climb up Mount Baldy, Sagan lost the overall lead to Julian Alaphilippe, however he put in a surprisingly strong performance to end the day two seconds behind Alaphilippe in the overall standings, and giving him a chance of taking the general classification through time bonuses on the final stage. He took a second out of Alaphilippe's lead in the intermediate sprint on the last stage to Pasadena, before pipping Tyler Farrar for third place on the finish line, taking a four-second bonus which gave him the overall win by three seconds.