The game's title is written out as Donkey Kong Junior in the North American arcade version and various conversions to non-Nintendo systems.

Enemies include "Snapjaws", which resemble bear traps with eyes; bird-like creatures called "Nitpickers", some of which can attack by dropping eggs; and "Sparks" which roam across the wiring in one of Mario's hideouts.

In the fourth stage, DK Jr. must push six keys into locks on the topmost platform to free Donkey Kong.

Several enemies attack Donkey Kong Jr., but he escapes them and makes it to his father, releasing him from the chains as Mario falls to the ground.

During Donkey Kong’s development in 1981, Shigeru Miyamoto's team had come up with several ideas and complete levels that would not fit into the game.

The conversation happened around the same time that Nintendo wanted another Donkey Kong coin-op to capitalize on the original's popularity, giving Miyamoto the opportunity to explore his newly established franchise.

Originally, Miyamoto wanted the new game to star Donkey Kong himself, but there were problems with the character's large size.

Since they still wanted a big Donkey Kong on top of the screen, they came up with the plot of Mario capturing him after the events of the first game.

He compared it favorably with another ColecoVision arcade conversion released at the same time, Sega's Space Fury, writing that Donkey Kong Jr. has better graphics and gameplay.

[11] Donkey Kong Jr. received an award in the category of "1984 Best Videogame Audio-Visual Effects (16K or more ROM)" at the 5th annual Arkie Awards, where the judges described it as "great fun", and noted that the game was successful as a sequel–"extend[ing] the theme and present[ing] a radically different play-action" than its predecessor, Donkey Kong.

Allgame gave a review score of 4 out of 5 stars praising the graphics and sound being "exceptionally arcade-like" and the controls and play mechanics being faithful to the arcade version.

[14] The NES version is also a playable game on Animal Crossing, though a special password is needed from an official website which is now no longer available.

[21] On September 3, at 1984 Arcade in Springfield, Missouri, Mark L. Kiehl of Enid, Oklahoma surpassed Wiebe's record with a score of 1,147,800.

Host Geoff Edwards noted that he had the arcade machine in his dressing room and found the game to be highly difficult.