The Catechism in Questions & Answers

493. Are baptisms performed in other Christian denominations valid?

Yes, the dispensation of Holy Baptism with water is possible and effective in all parts of the one church of Christ. Baptism with water is the first step on the way to perfect redemption. Wherever believers are baptised with water and in the name of God, the Father, the Son, and the Holy Spirit, the baptism is valid. Baptism with water has been entrusted to the church as a whole. The reason for this lies in God’s universal will to save.

The church of Christ: see Question 365. et seq. Redemption: see Questions 89.-90., 108.-109., 215.-216.