The substitute struck nine minutes after coming on at halftime to ensure Poland finished second in the standings on seven points, level with Germany, and they will play Switzerland in the last 16.
Blaszczykowski received the ball on the right side of the penalty area and cut inside cleverly before hitting a sweet left-foot shot into the far corner of the net.
Ukraine finished bottom of the group with no points.
(Reporting by Ed Osmond; Editing by Toby Davis)
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