Simpson claimed a combined £186,626 in pay and benefits, including a salary of £97,027 and benefits totalling £89,599, for his final full year in office.
Simpson's total remuneration exceeded that of fellow joint general secretary Tony Woodley, who collected a salary of £93,815 and benefits of £28,293, by almost £65,000.
The reason for the large difference between the benefits claimed by Unite's former joint general secretaries is currently unclear, although it could be linked to Simpson's age.
Simpson's tenure was extended beyond the retirement age of 65 when he was re-elected in March 2009, meaning his benefits for his final year in office may have been boosted by the commencement of his pension payout.
Simpson and Woodley both retired in January 2011, when Unite's new general secretary Len McCluskey took over the reins of Britain's largest union.
A spokesman for Unite said: "As far as we are concerned, Derek Simpson has retired and Len McCluskey gets nothing like that figure."
Simpson and Woodley's pay was revealed by the TaxPayers' Alliance (TPA) in its annual Trade Union Rich List, which included information on the 37 union bosses who took home more than £100,000 in salary and benefits in 2009/10.
