Tregelles announced in May last year that she would leave Mencap in the autumn after 22 years with the charity, the past six as chief executive.
She succeeds Chris Simmonds, who is leaving Revitalise after almost 10 years in the role. A spokesman for the charity said Simmonds's next move had not been announced but he would be supporting the charity during the handover until he leaves in February.
Revitalise, which had an income of £9.3m in the year to the end of January 2019 and employs about 200 staff, is a much smaller charity than Mencap, which has an annual income in excess of £200m and has more than 8,000 staff.
Mindy Sawhney, chair of Revitalise, said Tregelles would bring a “wealth of knowledge” to the charity.
“It is an exciting time for the charity as we make bold changes in our holiday centres, improve the experience for our wonderful guests and plan the future for our pioneering work,” she said.
Tregelles, who joined Revitalise last week, said: “Since stepping down from Mencap in the autumn I have been looking for an exciting new opportunity to use my background and skills.
“I was heartened by Revitalise’s warmth and passion for creating unforgettable holidays for disabled people and carers.”
Revitalise runs three fully accessible holiday centres in Chigwell in Essex, Southport in Merseyside and Southampton, Hampshire.