Since its launch on April 1, 1979, and throughout the 1980s, Nickelodeon aired programs for preschoolers (most prominently Pinwheel and Today's Special) on weekdays from 8:00 am – 2:00 pm and weekend mornings.

On weekends, preschool programs aired at earlier hours of the day, and in the case of Eureeka's Castle went unbranded.

On April 5, 1993 (1993-04-05), Nick Jr. premiered a new series, Cappelli & Company, and received a new rebrand which prominently featured a new logo consisting of an orange parent and a blue child, and the slogan Grow, Learn, and Play.

Nick Jr. began to invest more into producing original interstitial series (including 1994's Muppet Time, forty two-minute shorts from The Jim Henson Company) in order to stay within a self-imposed limit of five minutes of commercials per hour.

In the context of his segments, Face was capable of materializing objects such as an astronaut, a robot, a clown, a window, a traffic light, stars, and even wood.

He was also capable of creating a number of Foley sound effects and voices including an iconic signature three-note trumpet noise usually following the name "Nick Jr." at the end of almost every bumper.

In 1995, Nick Jr. acquired broadcast rights to The Busy World of Richard Scarry from sister network Showtime, and later premiered Rupert on September 11 and Little Bear on November 6 (both were produced by the Canadian animation studio Nelvana).

Rugrats was pushed out of Nick Jr.'s lineup after May 2, 1997, to make room for second showings of Little Bear and Blue's Clues.

In the first quarter of 1999, Nick Jr. premiered three new series based on books, Franklin on January 11, and Kipper and Maisy in February, which helped increase the block's ratings.

Nick Jr. briefly aired reruns of Shining Time Station beginning June 5, 2000 (Maggie and the Ferocious Beast premiered on the same day) to promote the film Thomas and the Magic Railroad, before replacing it with Dora the Explorer on August 14, which became one of Nick Jr.'s most successful series.

In the spring of 2002, Nick Jr. altered the format of its commercial breaks, resulting in the removal of older network IDs dating back to 1994.

Beginning on January 10, 2003, Dora the Explorer and Blue's Clues were placed in Nick Jr.'s "Play Along Time" sub-block.

On September 1, 2003 (2003-09-01), Nick Jr. received a rebrand that introduced more than a dozen new logos; British program Rubbadubbers premiered the next day.

[5] On October 11, 2004 (2004-10-11), Nick Jr. received another rebrand containing interstitials co-produced with Little Airplane Productions featuring the block's new mascot Piper O'Possum (voiced by Ali Brustofski and created by Josh Selig), and the new slogan "Love to Play!".

Nick Jr.'s commercial limit increased to 8 minutes per hour, and the block began airing more interstitials that were clips from its' shows.

The block's new branding was designed by Melinda Beck, and many bumpers featured drawings, finger puppets or cupcakes.

The Nickelodeon splat logo was edited onto the block's split-screen credits design and interstitials predating the brand.

On the same day, the Nick Jr. block also began to use Nickelodeon's on-screen credits to include more commercials (now 12 minutes per hour).

From 2002 to 2004, it was part of the general Nick on CBS block, which also included programming from the main Nickelodeon channel.

It ended after Viacom and CBS Corporation were separated at the start at 2006 (but re-merged in later years) and was replaced by the KOL Secret Slumber Party block on September 16, 2006.

On April 5, 2008, competing Spanish network Univision added Spanish-dubbed versions of Dora the Explorer and its spin-off Go, Diego, Go!

For a brief time in summer 2010, Tr3s, a sister network to Nickelodeon, aired a daily block of Spanish-dubbed Nick Jr. programs under the name Tr3s Jr. to meet E/I requirements for its broadcast affiliates.

In October 2015 for the Halloween/Nick or Treat season, the "Face the Monster" bumper would play on the block as a transition of introducing episodes of Aaahh!!!