This retrospective study compared clinical, radiological, and patient- and clinician-reported outcomes between immediate and delayed implants placed in patients with tooth agenesis as part of one-stage implant therapy with a split-mouth design. A total of 12 sites of permanent tooth agenesis in five patients received 12 implants (2.4 implants per patient), six being immediate implants in deciduous teeth post-extraction sites, and six being late implants replacing already extracted or spontaneously lost deciduous teeth. Data reporting was performed descriptively without statistical comparative analysis between study groups. Radiographic crestal bone level changes between the time of surgery and 1-year post-surgery did not indicate any marked difference between treatment groups. Patient-reported outcomes related to post-surgical pain and patient preference indicated less pain in immediately treated sites, resulting in a corresponding patient preference related to this treatment modality. Clinician-rated satisfaction levels did not differ. The results of this pilot study support the use of immediate implant placement as a suitable procedure in cases of tooth agenesis.