|Date of birth||22 December 1975|
|Place of birth||Gdynia, Poland|
|Height||1.85 m (6 ft 1 in)|
|1995||→ Łódzki KS (loan)||16||(6)|
|* Senior club appearances and goals counted for the domestic league only and correct as of 12 October 2016
‡ National team caps and goals correct as of 12 October 2016
Mięciel started his football career at Wisła Tczew for which he played until 1990. The next stop in his career was Lechia Gdańsk. In December 1993 he transferred to Hutnik Warszawa but after only six months he moved on to local rivals Legia Warsaw where he played until 2001 (only interrupted by a half year loan to ŁKS Łódź in 1995).
After a disappointing season at Borussia Mönchengladbach Mięciel went on to Greece. His first stop was Iraklis Saloniki. After two and a half seasons, he moved to local rivals PAOK. He scored five goals in 13 games till the end of the 2004–05 season. In his second season, he scored five times in 25 matches. His most successful season was 2006–07: in 29 matches he notched 14 goals. He was one of the topscorers in the Greek league and PAOK's "most valuable player" of that season.
After his first disappointing attempt in the German Bundesliga with Borussia Mönchengladbach Mięciel returned for the 2007–08 season, this time to play for VfL Bochum. The transfer fee was estimated at 250,000 euros. For the 2009–10 season he returned to Legia Warsaw on a free transfer. For the 2010–11 season he returned to Łódzki KS on a free transfer.
- I liga: 2010–11
- Topscorer of PAOK: 2006–07
- Most Valuable Player of PAOK: 2006–07