Senna attracted the attention of Formula One teams Williams, McLaren, Brabham and Toleman, all of whom he tested for. Neither Williams nor McLaren had a vacancy for the 1984 season. His name was linked to Brabham’s second seat, but Brabham’s lead driver, double world champion Nelson Piquet, preferred his friend Roberto Moreno, while title sponsor Parmalat wanted an Italian driver. His only option was to join Toleman—a relatively new team using less competitive Pirelli tyres—replacing Derek Warwick. Venezuelan Johnny Cecotto was his team mate.

Senna made his debut at the Brazilian Grand Prix in Rio de Janeiro. He scored his first World Championship point in his second race at the South African Grand Prix with severe muscle spasms, replicating that result two weeks later at the Belgian Grand Prix. A combination of tyre issues and a fuel pressure problem resulted in his failure to qualify for the San Marino Grand Prix, the only time this happened during his career. Senna’s best result of the season came at the Monaco Grand Prix, the first wet weather race of the season. Qualifying 13th on the grid, he made steady progress in climbing through the field, passing Niki Lauda for second on lap 19. He quickly began to cut the gap to race leader Alain Prost, but before he could attack Prost the race was stopped on lap 31 for safety reasons, as the rain had grown even heavier. At the time the race was stopped Senna was catching Prost at 4 seconds per lap. Senna finally passed Prost during the 32nd lap at the end of which the red flag was shown. However according to the rules, the positions counted were those from the last lap completed by every driver, lap 31, at which point Prost was still leading. Senna’s second place was his first podium in Formula One, and his performances in rainy conditions became a hallmark of his career.

It is perhaps this race that planted the seed for future clashes between Senna and the FIA French president, by Jean-Marie Balestre, which saw Senna being the subject of unfavorable decisions against him. Indeed, commentators in 2010′s “Senna – The Movie” refer to a very political sport and the 1984 Monaco Grand Prix being stopped to favour and protect Alain Prost—a French driver on a basically French territory—losing to a novice driver.

Still in 1984, Senna took two more podium finishes that year—third at the British and Portuguese Grands Prix—and placed 9th in the Drivers Championship with 13 points overall. He did not take part in the Italian Grand Prix after he was suspended by Toleman for being in breach of his contract by signing for Lotus for 1985 without informing the Toleman team first.

Senna also raced in two high-profile non-Formula One races in 1984: The ADAC 1000 km Nürburgring where, alongside Henri Pescarolo and Stefan Johansson, he co-drove a Joest Racing Porsche 956 to finish 8th, as well as an exhibition race to celebrate the opening of the new Nürburgring, which was attended by several Formula 1 drivers, each driving identical Mercedes 190E 2.3–16. Senna won from Niki Lauda and Carlos Reutemann. After the race Senna was quoted as saying, “Now I know I can do it.”