尖叫要塞 2017（Scream Fortress IX）是一次于2010年10月27日补丁发布的主要更新兼万圣节活动。这次活动引进了17 份万圣节合同，并且所有玩家都能通过合同追踪器免费完成。除此以外，原先的所有尖叫要塞地图也全都回归了。
On 2017年10月27日补丁 the Case Global Unusual Effects were updated to draw from a pool of previous years' Halloween Unusual effects during the event.
On 2017年10月31日补丁 the Taunt Unusualifiers were updated to draw from a pool of previous years' Halloween Unusual effects during the event.
The Halloween Contracts were removed from the ConTracker before 12:00 UTC of November 9. Halloween cosmetics and the Soul Gargoyle remained active until 12:00 UTC of November 10.
This Scream Fortress event offered 17 Halloween Contracts. They were free Contracts and did not require a Jungle Inferno Campaign Pass. These Halloween Contracts are different from the Merasmissions used in the previous Scream Fortress 2016 and Scream Fortress 2015. Not only are they different in their objectives, but they are also different in that they were accessed through the ConTracker (in a folder labeled "Halloween") in the same manner as the other Contracts activated in the Jungle Inferno Campaign. However, when completed, these Halloween Contracts were counted as Merasmissions by the Soul Gargoyle.
This set encouraged and rewarded exploration of all Halloween maps, with exception on Ghost Town, confrontation of all boss challenges, and exercise of all current Halloween map features, including Halloween pumpkins, pumpkin bombs, magic spells, bumper cars, and Underworlds.
Three of these Contracts were dedicated to defeating bosses, seven to the released community Halloween maps of previous years, and six to the Valve-made Halloween maps. Additionally, there is a "Start" contract, which could be completed on any map within Casual Mode.