He has agreed to remain with the company while it begins its search for a replacement and an orderly handover can be completed.
Sinclair joined the firm in 2012 as group financial controller and was promoted to CFO at the start of 2014.
Douglas McCormick, chief executive officer said: “I would like to thank Patrick for his considerable contribution to Sweett Group over the last three and a half years.
He has actively participated in the successful delivery of a number of strategic objectives for the group, and has been instrumental in managing the financial performance of the business. We wish him every success for the future.”
Sinclair leaves after Sweett has emerges from a torrid past year. It fell £1.1m into the red last year after difficult trading in the Middle East and exceptional administrative costs related to a serious fraud investigation that led to a conviction for bribery at its Middle East division.
It is closing its Middle East business after completing the sale of its Far East and India operations to focus on Europe and North America.