Lacey, previously sales director at organic babyfood company Plum, has set out his stall to increase the petfood company's share to at least 2% of the £2.4bn UK market.
The UK was a nation of pet lovers where many people substituted pets for children," he said. "Customers want their pets to eat a healthy, balanced diet," he added.
"I have joined at a really exciting time in the development stages of Lily's Kitchen. With the brand turning over a 173% sales increase on last year, it is evident the organic petfood market is on the up."
Henrietta Morrison, the founder of Lily's Kitchen, added: "With his extensive experience in the babyfood boom, I am confident that Simon will turn the petfood market on its head."