Does the Roman Catholic church recognize LDS baptisms? According to some of the answers in this question, the Roman Catholic church recognizes baptisms that use water and follow the Trinitarian formula, even if they are not performed by a Catholic.

Baptisms in The Church of Jesus Christ of Latter-day Saints are performed in the name of the Father, Son, and Holy Spirit as follows:


  “The person who is called of God and has authority from Jesus Christ
  to baptize, shall go down into the water with the person who has
  presented himself or herself for baptism, and shall say, calling him
  or her by name: Having been commissioned of Jesus Christ, I baptize
  you in the name of the Father, and of the Son, and of the Holy Ghost.
  Amen.
  
  ”Then shall he immerse him or her in the water, and come forth again
  out of the water.“


Source: Doctrine and Covenants 20:73–74. see also 2 Nephi 31, 3 Nephi 11, and  Handbook 2, 20.3.8.

Therefore, does the Roman Catholic church recognize LDS (Mormon) baptisms as valid, or would a Latter-day Saint need to be re-baptized to become a Catholic?
For Baptism to be valid requires three things: form, matter and intention.

Form refers to the words, which must refer to baptism in the name of the Father, Son and Holy Ghost. LDS baptism meets this criteria.

Matter requires the use of water. LDS baptism meets this criteria.

The Intention must be to do what the Church does. For this reason baptism in other Christian churches, or by lay persons, or even by non-Christians is valid if the intention is to do what the Church does. A baptism in a play at a theatre, or by children horsing around in a pool,  would not be valid as the Intention would not be there. A baptism by a lay catholic against canon law would be illicit but not invalid, provided it was deliberate and intentional.. 

In July 2001 the Vatican Congregation for the Doctrine of the Faith declared that the LDS (Latter Day Saints also called Mormon) understanding of Baptism was so different from the Catholic understanding that the intention was not the same.  The congregation said that the Catholic Church could not accept Mormon belief that "God the father had a wife, the Celestial Mother, with whom he procreated Jesus Christ and the Holy Spirit." Therefore the Roman Catholic Church believes that when Mormons baptise they are not intending to baptise into the Christian Faith, as understood by Rome.

Two out of three is not enough.

So, no the Roman Catholic Church does not recognise LDS baptism as valid. A Mormon is able to receive Catholic Baptism and, if wishing to become Catholic, must do so.