This description of Route 117 follows it from the south-east to north-west direction. Route 117 starts in Montreal at the Decarie Interchange where Autoroute 40 and Autoroute 15 meet. Montrealers sometimes unofficially extend Route 117 south along the portion of Decarie Boulevard that runs parallel to the Decarie Expressway. , Quebec.From the Decarie Interchange Route 117 goes north on Boulevard Marcel-Laurin,, and Laurentian Boulevard in Cartierville, crossing the Rivière des Prairies over the Lachapelle Bridge to Île Jésus, continuing through the Laval communities of Chomedey, Fabreville and Sainte-Rose, north bound as Boulevard Curé-Labelle, Boulevard Chomedey at the former Chenoy's deli, left turn at Boulevard Cartier and back into Boulevard Curé-Labelle, south bound as Boulevard Curé-Labelle. At the Rivière des Mille Îles, it crosses over the Marius Dufresne Bridge to the "North Shore". From here Route 117 runs parallel to Autoroute 15 until Sainte-Agathe-des-Monts, going through the Laurentian mountains. Towns along the route in this section include:
Rosemère
Sainte-Thérèse
Blainville
Mirabel
Saint-Jérôme
Saint-Jérôme
Saint-Jérôme
Prévost
Piedmont
Sainte-Adèle
Val Morin
Val-David
Sainte-Agathe-des-Monts
After Sainte-Agathe-des-Monts, Route 117 continues as a four-lane divided highway winding its way through Laurentides Regional County Municipality until it reaches the town of Labelle. From this point on to the Ontario border, Route 117 is mostly a standard 2-lane highway. In Grand-Remous, Route 117 crosses the Gatineau River and intersects with Route 105 which goes south-west to Maniwaki and Gatineau. Towns along the route in this section include:
. From Grand-Remous, the route heads north, travelling some 220 km through undeveloped wilderness, most of it part of La Vérendrye Wildlife Reserve. While the reserve is popular for a variety of outdoor activities, services along the road are sparse. This section is often considered as one of the most dangerous routes in the province due to numerous fatal accidents, some involving tractor-trailers. During the winter, the route is often extremely slippery, even during dry and clear days. The few communities along this section are:
After the intersection with Route 113, Route 117 heads west to Ontario where it becomes Highway 66. The section between Rouyn-Noranda and Arntfield runs concurrent with Route 101. Towns along the route in this section include: