Planes at Frankfurt airport, Europe's third busiest, "were not in the right place and cabin crew unavilable" after the strike ended on Friday, the spokesman said, adding that a return to normal air traffic was expected by later in the day.
Luftansa confirmed in a statement posted online that 18 flights had been cancelled.
Friday's strike had forced the airline to ground 190 of 360 flights, mostly short and medium-haul flights to Germany and the rest of Europe.
In all, a total 26,000 passengers were affected.
The UFO labour union, which represents some two-thirds of Lufthansa's 18,000 cabin crew members, said participation was "very high".
The union had called the eight-hour strike in its fight for a five percent pay increase for cabin crew for 15 months backdated to January this year after three years of zero increases.
It is also opposed to the use of temporary cabin staff in Lufthansa aircraft.
Unions had held off from strike action while last-ditch wage negotiations were still under way, but with no breakthrough, UFO declared the talks had failed and called for immediate walkouts.
Lufthansa, whose latest offer was for a pay increase of around 3.5 percent, has urged unions to return to the negotiating table.
UFO says it will not rule out further strike action.