Mario's Early Years: Fun With Letters is a collection of letter-related activities for kids ages 3 to 6 hosted by Mario and Co. Playing with either Mario or Princess Toadstool, you select from 10 different activity "worlds" each filled with different activities that range from letter recognition to sentence fill-in, letter-sound recognition, vowel recognition, etc. Each activity can be played in either Discovery mode, where you are free to do what you wish, or in Learning mode, where Luigi guides you through the activities.
The game also includes a Parent's Information Center, which explains what each of the activities does and how to complement them. Options to configure the activities to each parent's wishes are also provided.