A diagnosis of unexplained infertility is commonly made when clinical investigations fail to identify any obvious barriers to conception. As a consequence, unexplained infertility includes several heterogeneous conditions, one being women with age-related infertility. However, the latter represent a peculiar and different situation. Women with age-related infertility may have a different prognosis and may benefit from different treatments. Unfortunately, since fecundity declines with age, discerning between unexplained infertility and age-related infertility becomes more and more difficult as the woman's age increases. In this opinion, with the use of a mathematical model we show that the rate of false positive diagnoses of unexplained infertility increases rapidly after 35 years of age. Using a threshold of 2 years of unfruitful, regular unprotected intercourse, this rate exceeds 50% in women starting pregnancy seeking after 37 years. The scenario is much worse using a threshold of 1 year. From a clinical perspective, extrapolating results obtained in a population of young women with unexplained infertility to those with age-related infertility is not justified. It is noteworthy that, if Assisted Reproductive Technologies are unable to overcome age-related infertility, the older women erroneously labeled with unexplained infertility may receive inappropriate therapies. These may expose women to unjustified risks and waste financial resources. Unfortunately, the available literature about older women is scanty and does not provide valid evidence. Randomized controlled trials aimed at identifying the most suitable clinical management of older women with a normal infertility work-up are pressingly needed.