TSS focuses on several markets including health-care and government.
Constellation will initially finance the euro250-million transaction with a US$350-million one-year term loan. Before the loan matures, the company expects to refinance TSS on a stand-alone basis.
It expects the deal to close on Dec. 31, subject to standard conditions. TSS will then form a new operating group within Constellation.
Constellation shares have been on a fairly steady upward trajectory for several years and have nearly doubled in value since their low point of the year.
On Monday, the stock shot up $10.19, or 6.19 per cent, to $206.69 on the Toronto Stock Exchange, almost double its 52-week low of $111.09 set in February.