Image credit: Eurosport
Nieminen actually broke Djokovic's serve in the very first game of the match, but Novak bounced back to take a straight-sets victory.
The top seed appeared distracted in a performance littered with loose serves and uncharacteristic errors.
The final result was 6-4 6-2 6-3 in the Serb's favour as he continues on in the grass-court event.
Serb Djokovic was still far too good for 33-year-old world No 92 Nieminen who was playing in his final Wimbledon.
The defending champion broke in the sixth game of the third set and completed victory when Nieminen sent a forehand wide.
Djokovic will play Australian Bernard Tomic, the 27th seed, in the last 32.
Bradley Wiggins (Stage 20, 2012)