Background: Despite undeniable evidence for the efficacy and effectiveness of Cognitive Behaviour Therapy for Insomnia (CBT-I), the potential for its widespread dissemination and implementation has yet to be realised. A suggested reason for this is that traditional CBT-I is considered too burdensome for deployment, in its current form, within the context of where it would be most beneficial—Primary Care. One strategy, aimed to address this, has been to develop briefer versions of CBT-I, whilst another has been to deliver CBT-I in a group format. An alternative has been to attempt to address insomnia during its acute phase with a view to circumventing its progression to chronic insomnia. The aim of the present study was to compare a brief version of CBT-I (one-shot) when delivered individually or in groups to those with acute insomnia. Method: Twenty-eight individuals with acute insomnia (i.e., meeting full DSM-5 criteria for insomnia disorder for less than three months) self-assigned to either a group or individual treatment arm. Treatment consisted of a single one-hour session accompanied by a self-help pamphlet. Subjects completed measures of insomnia severity, anxiety and depression pre-treatment and at one-month post-treatment. Additionally, daily sleep diaries were compared between pre-treatment and at the one-month follow up. Results: There were no significant between group differences in treatment outcome on any sleep or mood measures although those in the group treatment arm were less adherent than those who received individual treatment. Furthermore, the combined (group and individual treatment arms) pre-post test effect size on insomnia symptoms, using the Insomnia Severity Index, was large (d = 2.27). Discussion: It appears that group treatment is as efficacious as individual treatment within the context of a “one shot” intervention for individuals with acute insomnia. The results are discussed with a view to integrating one-shot CBT-I in Primary Care.