Lactoferrin (Lf), which is particularly abundant in human breast milk during the early stages of lactation, provides protection against a variety of infections, including viral infections, and has demonstrated activity against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The objective of this study was to measure the concentrations of Lf in the colostrum of mothers with active coronavirus disease 2019 (COVID-19) infections during delivery, in mothers with a history of COVID-19 during pregnancy, and in non-infected controls. In this cross-sectional study, colostrum samples from 41 lactating mothers with a confirmed history of SARS-CoV-2 infection (asymptomatic or symptomatic) (both active and past infections) were collected. Twenty-eight colostrum samples collected during the pre-pandemic period served as a control group. An enzyme-linked immunosorbent assay was performed to analyze the Lf concentrations. Concentrations of Lf in the colostrum samples were closely related to virus infection. Colostrum samples from mothers with confirmed SARS-CoV-2 infections contained higher concentrations of lactoferrin compared with samples from mothers from the control group. The highest concentrations of Lf were found in the colostrum samples of mothers with active SARS-CoV-2 infection during delivery when compared with the post-infection and control samples. This observed increase in lactoferrin suggests that it may be an important protective factor for breastfed infants, a finding which was particularly relevant during the pandemic period and remains relevant whenever a breastfeeding mother is infected.