The courting season of the western capercaillie starts according to spring weather progress, vegetation development and altitude between March and April and lasts until May or June. Three-quarters of this long courting season is mere territorial competition between neighbouring cocks or cocks on the same courting ground.

At the very beginning of dawn, the tree courting begins on a thick branch of a lookout tree. The cock postures himself with raised and fanned tail feathers, erect neck, beak pointed skywards, wings held out and drooped and starts his typical aria to impress the females. The typical song given in this display is a series of double-clicks like a dropping ping-pong ball, which gradually accelerate into a popping sound like a cork coming of a champagne bottle, which is followed by scraping sounds.

It is only towards the end of the courting season that the hens arrive on the courting grounds, also called leks, meaning play inNorwegian. Now the cocks continue courting on the ground, this is the main courting season.

The cock flies from his courting tree to an open space nearby and continues his display. The hens, ready to get mounted, crouch and utter a begging sound. If there is more than one cock on the lek, it is mainly the alpha-cock who copulates with the hens present. In this phase western capercaillies are most sensitive against disturbances and even single human observers may cause the hens to fly off and prevent copulation in this very short time span where they are ready for conception.

As traditionally known by hunters, on the other hand, cocks are particularly refractory to otherwise alarming signs during their courting display. This originated a well-known reference to the species in popular culture: in one of the famous films starringRomy Schneider, young Empress Sissi goes hunting with her father. When he pauses to shoot a male western capercaillie taking advantage of his apparent numbness, she manages to scare away the bird. This is used as a metaphor for the changes brought about by her womanhood: being herself in love, her newfound awareness of the associated sense of rapture enables her to empathize with the hapless bird (as a younger girl she would have been simply excited by the prospect of a fine hunting trophy).

There is a smaller courting peak in autumn, which serves to delineate the territories for the winter months and the next season.

About three days after copulation the hen starts laying eggs. Within 10 days the clutch is full, the average clutch size is eight eggs but may amount up to 12, rarely only four or five eggs. The subsequent breeding lasts about 26–28 days according to weather and altitude.

At the beginning of the breeding season the hens are very sensitive towards disturbances and leave the nest quickly. Towards the end they tolerate disturbances to a certain degree, crouch on their nest which is usually hidden under low branches of a young tree or a broken tree crown. As hatching nears hens sit tighter on the nest and will only flush from the nest if disturbed in very close proximity. Nesting hens rarely spend more than an hour a day off of the nest feeding and as such become somewhat constipated. The presence of a nest nearby is often indicated by distinctively enlarged and malformed droppings known as "clocker droppings". All eggs hatch in close proximity after which the hen and clutch abandon the nest where they are at their most vulnerable. Abandoned nests often contain "caeacal" droppings'; the discharge from the hens appendixes built up over the incubation period.

After hatching the chicks are dependent on getting warmed by the hen. Like all precocial birds the young are fully covered by down feathers at hatching but are not yet able to maintain their body temperature which is 41 °C (106 °F) in birds. In cold and rainy weather the chicks need to get warmed by the hen every few minutes and all the night.

They seek food independently and prey mainly on insects, like butterfly caterpillars and pupae (there is a specialised butterfly species whose caterpillars develop only on Vaccinium myrtillus), ants, myriapodae, ground beetles and the like.

They grow rapidly and most of the energy intake is transformed into the protein of the flight musculature (the white flesh around the breast in chickens). At an age of 3–4 weeks they are able to perform their first short flights, from this time on they start to sleep in trees in warm nights. At an age of about 6 weeks they are fully able to maintain their body temperature. The down feathers have been moulted into the immature plumage and at an age of 3 months another moult brings them in their subadult plumage and now the two sexes can be easily distinguished.

From the beginning of September the families start to dissolve. First the young cocks disperse, then the young hens, both sexes may form loose foraging groups over the winter.