After the TSB acquisition, 22% of Sabadell's assets will be located outside Spain, compared with 5% at present.
The deal, worth £1.7 billion, saw Lloyds sell its 50% stake in the bank.
In January, TSB opened up its intermediary channel, which it announced as "the next step in the bank's growth strategy which aims to ‘shake up’ the broker market".
Josep Oliu, Chairman of Sabadell, said:
"Today marks the beginning of a major project. This is a milestone that enables us to enter a market with vast opportunities. We do so in partnership with a well-positioned challenger bank with a prestigious brand backed by a long tradition.
"Furthermore, TSB has a highly professional management team which is successfully delivering its business plan and which is committed to growing TSB further still as part of the Sabadell Group. TSB will enable us to increase our international footprint and diversify our business activities. It's a major opportunity."
Paul Pester, CEO of TSB, added:
"The deal with the Sabadell Group is a major vote of confidence in TSB. With the extra firepower and fresh perspective of Sabadell, TSB will be stronger and even better placed to build on its position as Britain's challenger bank. Being part of the Sabadell Group will help TSB bring more competition to the UK market more quickly and help us break the stranglehold the 'Big Five' banks have had for far too long."
