The unit was created at the end of 1936 in Villarrobledo with Lieutenant Colonel of Infantry Germán Madroñero López [es] as its commander and Manuel Simarro Quiles of the PSOE as its political commissar.

In mid-January 1937, the 17th Mixed Brigade was sent to the front lines, being deployed in the municipality of Ocaña to participate in a planned offensive on Brunete that, in the end, never took place.

[1] On 7 February, it was added to the Burillo group and, in the middle of the Battle of Jarama, was assigned to the defense of the Puente de Titulcia bridge; shortly thereafter, it was assigned to the Chorda group and was entrusted with the defense of the Puente de Pindoque bridge.

The 17th Mixed Brigade, now in its barracks in Morata de Tajuña, remained under the command of Lieutenant Coronel Julián del Castillo Sánchez [es], veteran of the Cuban War of Independence.

At the end of 1937, Militia Major Carlos Fabra Marín [es] assumed command of the brigade.