The deal, for an undisclosed sum, is likely to cap a bumper payday for SCS' five owners. The partners will stay with the firm to "continue to develop it".
TP Icap said it funded the acquisition in cash with earn-outs payable over the next five years.
Founded in 1991, SCS has a network of 26 brokers, specialising in crude oil futures, soft commodities, petroleum and refined products, natural gas options and crude oil options.
Given the size of the deal, no external financial advisers were engaged.
For the year ended 31 December 2016, SCS made revenues of $14.3m (£10.1m) and profits before tax of $0.8m. At 31 December 2016, it had gross assets of $4.2m.
The acquisition will provide a boost to TP Icap, which warned on challenging market outlook in at the end of last year alongside the departure of its finance chief.
In November Tp Icap bought smaller Marylebone-based rival Coex Partners in a deal worth an initial £7.1m.