Leyland marketing manager Sharon Hendry said: "Simon's visit represents the official unveiling of our darts sponsorship with him, and we couldn't be happier to be putting our name on his shirt for the year.
"Simon's performances in the world championships have already generated huge exposure for us in a matter of weeks and if this is a sign of things to come, then we can look forward to a sustained success story in a brand new arena for us."
Mr Whitlock, recently confirmed as a Premier League player for 2012, said: "I am thrilled to receive the support from Leyland. Having their backing at the World Championships seemed to push me on to perform well and I am sure I will be replicating this form in the competitions ahead."
Leyland will also be sponsoring 2008 British Darts Organisation world champion Mark Webster, as he bids to build on a breakthrough year in the PDC.
Aside from the sponsorship itself, both Mr Whitlock and Mr Webster will be making a number of personal appearances for Leyland, while incentives throughout the year mean customers will get the chance to see the pair play at future televised tournaments.
Leyland's Ms Hendry concluded: "More than 20% of the UK's population were exposed to darts in 2011 and it is now regarded as the second most popular sport on Sky behind football.
"With all this in mind, we couldn't be more excited to be involved with Simon and Mark, who we will be cheering on from now on!"