His first documented mention was on 21 October 1258, when he appears together with his father and two younger brothers in the consent of the foundation of a Cistercian abbey in Rudy.

His politics against Henry IV were reinforced when the Duke of Wrocław repudiated his wife Constance —sister of Mieszko— and sent her back to her homeland.

Mieszko refused to support any of the Piast pretenders to the Polish throne (Henry IV Probus, Przemysł II and Władysław I the Elbow-high).

On 17 January 1291 the formal agreement was signed in Olomouc which formed the alliance between the Bohemian Kingdom, Mieszko and his two brothers Casimir and Przemysław.

On 5 October 1305, Mieszko obtained his major victory when his daughter Viola Elisabeth married King Wenceslaus III.

This union was a chance for Mieszko to make himself one of the most powerful figures in Bohemia, and he even began some attempts to obtain the Polish crown.

However, Mieszko's promising career ended suddenly with the murder of Wenceslaus III (Olomouc, 4 August 1306).

The only sign of his political activities during this time was the lease of the Czech city of Kęty to the Bishop of Kraków, Jan Muskata, a strong opposer to the rule of Władysław I the Elbow-high in Greater Poland.

The Obituary of the Church of St. Vincent in Wrocław showed the existence of a certain "Grzymisława, Duchess of Opole" (Grimizlaua ducissa Opuliensis) who was buried there around 13 September 1286.