Tui is poised to create 175 jobs at its customer services centre in Swansea.
The Alexandra House office, which opened in 2015 with 48 staff, currently employs 280 people.
The travel group is to receive a £525,000 Welsh government business grant towards the expansion, the BBC reported.
Economy secretary Ken Skates said Wales’ customer service sector employed more than 30,000 people in 200 centres.
“The company’s expansion in Swansea is testament to our reputation for delivering excellence in customer service,” he said.
Tui said recruitment had started for advisors to help customers book their holidays.