Adult hippocampal neurogenesis (AHN) gives rise to new neurons throughout life. This phenomenon takes place in more than 120 mammalian species, including humans, yet its occurrence in the latter was questioned after a putative absence of neurogenesis markers in the adult human hippocampus was suggested. In this regard, we showed that prolonged fixation impedes the visualization of Doublecortin+ immature neurons in this structure, whereas a dilated post-mortem delay (PMD) has been suggested to underlie these discrepancies. Nevertheless, the individual and/or additive contribution of fixation and the PMD to the detection (or lack thereof) of other AHN markers has not been investigated to date. To address this pivotal question, we used a tightly controlled experimental design that included three groups of mice, two of which were subjected to artificially generated PMD of 6 h and 24 h, whereas a control group lacked any PMD. In those mice, the right hemisphere was fixed for 24 h whereas the left hemisphere was fixed for 2 months. This experimental design allowed dissecting the relative contribution of the aforementioned factors to the visualization of markers of individual AHN stages. Fixation emerged as the most prominent factor globally impeding the study of this process in mice. Moreover, the visualization of other especially sensitive epitopes was further prevented by prolonged PMD. These results are crucial to disambiguate current controversies related to the occurrence of AHN not only in human beings but also in other mammalian species.