At the same time as the Coupé, Fiat also introduced the convertible sporty two-seater Spider, with the original 843 cc engine tuned to produce 49 hp (37 kW) which allowed it to reach a top speed of 145 km/h (90 mph). The body was designed and built by Bertone. The folding roof section made of fabric could be stowed away completely under a rear flap. The Bertone design also featured smooth, essential lines and simple yet elegant details, such as the recessed headlamps equipped with tilted plexiglass covers to follow the lines of the wings, and the dihedral side panels inspired by Bertone's 1963 Corvair Testudo.
In 1968, Fiat revised the successful Spider and Coupé again and gave them an even stronger engine with 903 cc and 52 hp (39 kW). They were called Sport Spider and Sport Coupé. The Sport Spider body stayed essentially the same, but with a restyled front. The headlamps were moved forward slightly and the plastic covers were eliminated giving the car a "frogeye" look, and the original flush front turn indicators were replaced with units hung below the bumper. Several limited special edition versions of the Spider were offered, including the Racer featuring a body colored metal hard top and the Racer Berlinetta featuring a black vinyl hard top.