The 31-year-old new mother confirmed the deal on twitter.
Jessica Simpson is ''so excited'' about becoming a Weight Watchers ambassador.
The 31-year-old 'Fashion Star' mentor confirmed that she had signed a $4million deal with the diet plan brand on twitter yesterday (30.05.12).
She wrote: ''So excited to be part of the Weight Watchers family.''
She wrote on her Facebook page: ''The cool thing about the program is that it focuses on healthy habits for the long-term (and I can still indulge in my guilty pleasures every now and then, too). I have actually gotten a group of friends together who are going to be doing it with me.''
The 5ft 3in star is hoping to lose her baby weight within the year, according to reports.
A source told Us Weekly: ''As soon as Jessica heals from the C-section, she is extremely determined to get back in the gym and work out. She wants to show the world and is excited to do it.''
The insider added that she hasn't chosen a trainer yet.
They said: ''In fact, she hasn't even thought about working out for a year. But if she wants this, she'll need to work out a good five days a week.''