|Date of birth||20 September 1953|
|Place of birth||Nowa Sól, Poland|
|Height||1.86 m (6 ft 1 in)|
|Astra Nowa Sól|
|1971–1974||Dozamet Nowa Sól|
|* Senior club appearances and goals counted for the domestic league only|
After representing three clubs in his homeland he played out the remainder of his career in France and Portugal, winning seven major titles with Porto during his one-and-a-half-season spell.
Born in Nowa Sól, Młynarczyk arrived at Widzew Łódź in 1980 aged 27, after playing for three modest clubs. During his four-year spell, in which he was equally first and second-choice, the team won two Ekstraklasa titles, finishing second in the other two. In the 1982–83 European Cup, he helped Widzew to the semifinals after edging Liverpool in the last-eight (4–3 on aggregate).
In 1984, aged 31, Młynarczyk signed with SC Bastia in France. In January 1986 he switched countries again, joining FC Porto from Portugal, where he won the European Cup, the Intercontinental Cup and the UEFA Super Cup. After an interesting battle for first-choice status with Zé Beto, he eventually became the starter – he was in goal for all of these finals – but lost his importance after the emergence of 18-year-old Vítor Baía, choosing to retire from football in June 1989.
Młynarczyk started immediately working with Porto's goalkeepers after his retirement, a position he would also hold at former side Widzew Łódź. On 21 April 2008, he resigned after the latter side hired Janusz Wójcik as manager.
Młynarczyk won 42 caps for Poland during seven years, the first arriving in 1979 whilst in the ranks of lowly Odra Opole. He participated – always as starter – with the national team in two FIFA World Cups, 1982 and 1986, finishing in third place in the former edition and being ousted by Brazil in the round-of-16 in the latter.
Młynarczyk would also work as goalkeeping coach for the national team, before being replaced by Jacek Kazimierski.
- Primeira Liga: 1985–86, 1987–88
- Taça de Portugal: 1987–88
- Supertaça Cândido de Oliveira: 1986; Runner-up 1988
- European Cup: 1986–87
- Intercontinental Cup: 1987
- UEFA Super Cup: 1987
- "1988/89: FC Porto sem troféus e dez campeões europeus a chorar" [1988/89: FC Porto without trophies and ten European champions crying] (in Portuguese). Mais Futebol. 28 April 2014. Retrieved 11 May 2016.
- "Vítor Baía: a lenda nasceu há 30 anos" [Vítor Baía: the legend was born 30 years ago]. O Jogo (in Portuguese). 11 September 2018. Retrieved 18 October 2018.