GSK is the second largest pharmaceutical company in the world and the takeover of Pliva's research centre represents the largest investment in Croatia's science to date.
The work of the new research centre, that will employ 130 people, will be directed at finding new medicines for curing diseases, based on a thorough research of macrolytic antibiotics.
The vice president of the GSK drug discovery department, Patrick Vallance, said GSK invested eight million euros each day into drug discovery, adding that the centre in Zagreb would advance the company's scientific potential.
Present at the opening was British Ambassador to Croatia John Ramsden.