Despite extensive preparedness literature, existing studies fail to adequately explore healthcare graduates’ feelings of preparedness longitudinally across new graduate transition journeys, nor do they compare different healthcare professions to ascertain what opportunities exist for multiprofessional transition interventions. Therefore, this Australian study, underpinned by temporal theory, explores the preparedness transitions of medicine and pharmacy graduates. Our 6-month qualitative longitudinal study involved 12 medicine and 7 pharmacy learners after purposive sampling. They participated in an entrance interview before starting internship, longitudinal audio-diaries during their first three months of internship, and an exit interview. Framework analysis explored patterns in the data cross-sectionally and longitudinally for the whole cohort (thinking over time), with pen portraits illustrating individuals’ journeys (thinking through time). Preparedness and unpreparedness narratives involved practical skills and tasks, interpersonal skills, knowledge, and professional practice for medicine and pharmacy. However, narratives for practical skills and tasks, and professional practice were dominant amongst medicine graduates, while narratives for interpersonal skills and knowledge were dominant amongst pharmacy graduates. We found numerous cohort changes in feelings of preparedness over time, but the illustrative pen portraits demonstrated the complexities and nuances through time, including feelings of preparedness before internship becoming unpreparedness during internship (e.g., cannulas), improving preparedness through time (e.g., cover shifts), and persistent feelings of unpreparedness (e.g., patient interactions). While our cross-sectional findings are reasonably consistent with existing research, our comparative and longitudinal findings are novel. We recommend that educators build learners’ preparedness through uniprofessional transition interventions involving practical skills and tasks, and professional practice in medicine, and interpersonal skills and knowledge in pharmacy. More importantly, we recommend multiprofessional transition interventions for medicine and pharmacy learners before internship focusing on knowledge, and during internship focusing on practical skills and tasks.