Starches have been used to improve the textural properties, substitute fats or increase satiety in yogurts and acidified milk gels; however, studies involving the addition of flours are scarce. The objective of this study was to analyze the effect of skim milk substitution by pre-gelatinized extruded maize flour on the acidification process (changes in pH and rheology), textural properties, syneresis, and microstructure of acidified milk gels (15% w/w solids). To this end, pre-gelatinized flour was used to replace 17%, 33%, and 50% of the skim milk powder. A greater proportion of flour resulted in a faster acidification process and a higher pH at the gelation point, indicating a faster gelation. The substitution of milk by flour up to 33% increased the firmness and consistency of the set gel, but these changes were reversed with greater substitution levels due to the lack of a connected protein structure. In addition, a greater syneresis of the gels was observed as the milk content was reduced, an effect that was reversed by increasing the percentage of solids in the mixture.