Uefa has fined the Croatian Football Federation 25,000 euros (£20,200) for its supporters' behaviour during the Euro 2012 Group C match against Republic of Ireland.
Croatian fans let off flares during the 3-1 victory in Poznan on Sunday.
Stewards tackled one supporter who ran on to kiss coach Slaven Bilic.
"The sanction has been imposed for the setting-off and throwing of fireworks and missiles, and a pitch invasion by a supporter," a Uefa statement read.
Uefa is also investigating reports a banana was thrown on to the pitch during the Group C match between Italy and Croatia on Thursday.
A photographer reportedly saw a steward retrieving a banana and heard monkey chants directed at Italy striker Mario Balotelli.
Croatia face world and European champions Spain in the final Group C match on Monday in Gdansk. A win or a score draw of 2-2 or above guarantees Croatia passage to the last eight.