Prinoth entered Formula One competition in 1961, acquiring a Lotus 18 for use as a privateer in non-Championship Formula One events. The Lotus 18 was a well-regarded customer car of the era, widely used by private entrants seeking access to Formula One competition outside the championship rounds. Prinoth used it to contest a series of such events during 1961, and in two of these relatively minor races he achieved podium finishes — a noteworthy return for a privateer competing against the range of entries these events attracted.
His only formal attempt at a World Championship Formula One race came at the 1962 Italian Grand Prix at Monza. He entered with backing from Scuderia Jolly Club, an Italian motorsport organisation that supported several drivers during this period, but he failed to qualify for the race. With the field typically oversubscribed for Championship events, non-qualifying was a common outcome for privateer entrants whose machinery did not match the pace of factory teams and better-funded rivals. This Monza attempt remained his sole engagement with the World Championship proper.
He returned to Formula One in 1963 for two further non-Championship appearances, again at the wheel of his Lotus 18, the same car that had carried him through all his motorsport activity. In total, all of Prinoth's Formula One appearances were made in non-Championship events with the exception of the failed qualifying attempt at Monza.
Beyond his motorsport activity, Ernesto Prinoth founded Prinoth AG, a company that became a leading manufacturer of snow grooming machines used on ski slopes and cross-country trails worldwide. Snow groomers, which prepare and maintain the snow surface of pistes before and between ski runs, became increasingly important to commercial ski resort operations as the industry grew from the mid-twentieth century onward. The business Prinoth founded developed into a significant industrial enterprise, and the Prinoth name remained closely associated with the sector long after his death.
His son Erich Prinoth also pursued motor racing, competing in the Ferrari Challenge series.
Ernesto Prinoth's motorsport career was limited in scope, centred on non-Championship Formula One competition during the early 1960s without achieving a World Championship race start. His best results — podium finishes in non-Championship races — reflected a level of genuine competitiveness within the privateer field, even if they placed him at the margins of the sport rather than its centre. His wider legacy rests on the industrial enterprise he built, Prinoth AG, which became a far more visible presence in global commerce than his racing record. He died on 26 November 1981.