Monochroma is a cinematic 2.5D platformer with a silent narrative. The story is not explained, everything is shown through the imagery. The player controls a small boy through a monochrome environment, with dashes of red as the only colour highlights. Early on in the game, the boy's little brother breaks his leg and needs to be carried by the older one. Through different environments the boys need to overcome various obstacles and traps with environment and physics based puzzles to progress. The game starts in the countryside and then moves into the city and a corporation.
At the same time there is a larger narrative running in the background. In contrast to the theme of brotherly love, the game is set in a bleak, dystopian environment drenched in constant rain. There are very few people in the game and they often seem to be replaced with robots, who do not present an immediate threat. There are some enemies and chase sequences however.
The boy can run, jump, swing from chains and ropes, climb ledges, push and pull objects and levers etc. The helpless little brother is a part of the puzzles as well, as he needs to be carried and can only be put down in lighted areas as he is afraid of the dark. Movement is still possible while carrying the little brother, but then the older one can jump less high and far, meaning he often has to go on alone for a short time and then return for the little one. Puzzles often expand beyond the basic concepts, there are for instance explosive barrels on fire that are used for weight or temporary platforms, but can be put out by dragging them into the rain. Parts of the environment can be manipulated with levers and certain robots can be controlled for short sections. It is possible to die, there are sequences that need to be completed fast, and the game regularly creates checkpoints automatically. Optionally red flowers can be collected in hidden areas.