Techniques for insertion of supplementary content into a segmented content stream are described. In at least some embodiments, a content stream includes primary content, such as streaming web content, a movie, an event broadcast (live and/or recorded), a television program, and so on. The content stream can be segmented, such as via techniques for adaptive bitrate streaming. Techniques discussed herein enable supplementary content, such as an advertisement, to be inserted into the content stream. The supplementary content can be inserted at any specified time point, even if the specified time point falls within a segment of the content stream. Techniques further enable playback of the content stream to be paused during playback of the supplementary content, and to resume after playback of the supplementary content.