Neelam Makhijani, chief executive of the Resource Alliance, is to step down and return to India because her mother is ill.
The charity, which helps not-for-profit organisations improve in areas such as financial sustainability and runs conferences including the annual International Fundraising Congress in the Netherlands, said Makhijani would leave in May after more than four years in charge.
"It is with mixed emotions that I have decided to step down," said Makhijani. "It has been a huge honour to have held this post and to have been entrusted with the charity’s growth and development."
Jan Krol, chair of the Resource Alliance, said Makhijani had been instrumental in extending the reach of the organisation and strengthening its foundations for long-term development.
The alliance, which had an income of £2m in the year to the end of March 2013, said it would appoint an interim chief executive while a permanent replacement for Makhijani was sought.