Background: Cancer screening can reduce late-stage diagnoses, expand treatment options, and improve cancer outcomes. We modelled how introducing a multi-cancer early detection (MCED) screening programme in England could impact cancer treatment patterns. Methods: The proportions of cancers (19 types, diagnosed 2014–2019) treated with resection, radiotherapy, and systemic anti-cancer therapy (SACT) were applied to modelled stage-specific cancer incidence data with and without addition of MCED screening to existing screening. We modelled an initial screening round (first screen for individuals aged 50–79 years) and a steady-state programme (annual screening from age 50–79 years). Results: Assuming test parameters are accurate, if MCED screening is introduced in England, more cancers would require resection compared with current annual usage (steady-state: +8900, +10.0%). The number of cancers receiving radiotherapy would decrease overall (–1200; –2.0%) due to a decrease in palliative radiotherapy (–2100; –23.0%); the number of cancers treated with curative radiotherapy would increase slightly (+932; +2.1%). Fewer cancers would receive cytotoxic chemotherapy (–5300, –9.8%) and non-cytotoxic SACT (–530, –12.2%). Increased use of curative treatment combinations is also predicted. Conclusions: Changes to future service delivery and workforce planning will be needed for the full benefits of an MCED screening programme to be realised.