Sakon tested for the Jordan team on the Friday of the 2005 Japanese Grand Prix. However it wasn't until mid way through 2006 that he signed for the Super Aguri team as test/third driver.
Debut & Super Aguri (2006)
He replaced Franck Montagny (who had replaced Yuji Ide) following the French Grand Prix, and he competed the final 7 races of the 2006 season alongside Takuma Sato. After a poor start - he managed only 1 lap in his first two races - Sakon ended the season more strongly setting the 7th fastest time and 2nd fastest middle sector in Brazil.
This however wasn't good enough for him to secure a race seat with the team for 2007, which Anthony Davidson took, he did however remain as a test driver for the team.
With Christijan Albers being dropped from Spyker mid-2007, Sakon got a race seat for the remaining 7 rounds of the season with the Dutch team.
It wouldn't be harsh to say that Yamamoto struggled in F1 he never beat his teammate in a race, and only once (in 14 starts, albeit 6 retirements) managed to finish higher than last - second last in the 2007 Japanese Grand Prix.
On 17th April 2010 Sakon was confirmed as reserve and test driver to the new HRT squad.