Benet Middleton takes on a 70-strong department, which has been restructured for his arrival to include fundraising as well as campaigns and comms.
Middleton said he would be integrating the charity's communications functions and devising new ways to lobby for extra government service funding.
‘The recent Education Select Committee report cited NAS and autism throughout, so the organisation is already making a big impact,' he said.
‘We are one of the largest service providers in the voluntary sector and have an obligation to use that weight and experience to lobby for improved services and better public understanding.'
The 15,000-member charity, with a turnover last year of £65m, represents the two million people in the UK affected by the condition.
Middleton spent six years at Diabetes UK, overseeing its rebranding in 2000 and filling in as chief executive during 2004. He left earlier this year and was replaced in April by ex-Kensington and Chelsea Council communications director Penny Mordaunt.
He worked for the Consumers' Association from 1993 to 1999, writing initially for Which? magazine and latterly as head of policy, working on a range of the group's campaigns.
In May, NAS launched a campaign targeting the education sector to raise awareness of the needs of autistic children among the public and decision makers (PRWeek, 19 May).