Valentine's Day postcard, c. 1910The day is most closely associated with the mutual exchange of love notes in the form of "valentines", a practice that dates back to the rise of romantic love in Europe (14th century). Modern Valentine symbols include the heart-shaped outline and the figure of the winged Cupid. Starting in the 20th century, the practice of hand writing notes has largely given way to the exchange of mass-produced greeting cards. The Greeting Card Association estimates that world-wide approximately one billion valentine cards are sent each year, making the day the second largest card-sending holiday of the year behind Christmas. The association also estimates that women purchase approximately 85 percent of all valentines.

In the United States in the second half of the 20th century, the practice of exchanging cards has been extended to include the giving of all manner gifts, in a heterosexual relationship usually from the man to the woman. Such gifts typically include roses and chocolate. Starting in the 1980s, the diamond industry began to promote Valentine's day as occasion for the giving of fine jewelry.

A dinner date on Valentine's Day is often regarded as indicating that a dating couple are involved in a serious relationship.

In the United States the day has come to be associated as well with a generic Platonic greeting of "Happy Valentine's", which may be said by men to their female friends, but rarely to other male friends.