After leaving school, Paul studied hospitality and catering at Southampton City College. Whilst he was at college, Gary Rhodes invited students to work for him and, following a successful interview, Ainsworth began working for Rhodes in 1998 at his restaurant Rhodes in the Square. He then worked at Restaurant Gordon Ramsay for three years before moving to Ramsay's P'trus restaurant in 2003, working under Marcus Wareing for three years and continued to work for Wareing when he relocated to The Berkeley. Paul then opened his own restaurant ' Number 6. However, in 2009 Ainsworth bought out his business partners, taking over the business with his wife and, three years after opening, the restaurant was renamed Paul Ainsworth at Number 6. The restaurant was awarded a Michelin star in 2013 and its fourth AA Rosette in 2016. His peers have been hotly tipping Number 6 for a second Michelin star ever since. Ainsworth also oversees Padstow Italian restaurant Caffe Rojano in the Square which he reopened in 2011 and, along with his wife, runs The Townhouse guest house, also located in Padstow and in 2019 took over the lease of The Mariners Public House in Rock. 2023 saw Paul once again teaming up with his old boss Gordon Ramsay to appear on the TV show, Next Level Chef.