Impossible Mission II retains the same cast of characters as its predecessor while adding some new adventure elements, enemies, and hazards. A secretive soldier known as 4125 must infiltrate a massive base and collect three access codes from each tower and obtain a musical sequence code that will cripple Elvin Atombender's diabolical plans. As in the original, exploration and item retrieval mixes with elements of stealth and platforming.
Certain rooms contain items such as access codes for other rooms, and visual clues found in desks, cabinets, and bookcases. Access codes, when retrieved, can be entered into a terminal causing it to display a list of features. Correct codes can be used to stop robotic activities, maneuver select elevators, and place bombs in different locations. Robots and other drones roam about firing destructive lasers, throwing bombs and mines, and pushing 4125 off elevators and platforms.
While each screen is different, all contain puzzle-solving elements, and several contain a series of platform jumps, which must be successfully negotiated to continue. As the character finds important items and codes while exploring the base, screens become harder and enemies more hazardous. Later levels incorporate bombs, various lighting effects, and hidden mines into the mix. Although 4125 is alone, a special watch allows him to scan all areas of the complex, solve and decipher certain codes, activate and detonate bombs, and keep track of time.