After a slow start to the season, the Lotus 77 proved to be best of the rest behind Ferrari, McLaren and Tyrrell. Andretti worked hard to develop the car, and from mid season onwards, the 77‘s performance picked up. It was however best suited to tracks with long corners such as Anderstorp, where Andretti led easily before engine failure put him out. At Zandvoort and Mosport Park tracks he finished on the podium.

Colin Chapman vetoed Andretti‘s request to race the Lotus 78 at Zandvoort, so Mario reluctantly raced the 77 until the end of the season. The final race was run in monsoon conditions at Fuji Speedway in Japan. Andretti‘s car was very well set-up for the track, with the car set to its narrowest width and with virtually flat rear wing. Andretti drove a clever tactical race to win by a lap from Patrick Depailler and new world champion James Hunt. Andretti was glad to put the 77 aside to concentrate on developing the 78 for the 1977 Formula One season.