The 5’ cap structure is essential for the function of synthetic mRNA as vaccines and therapeutics. Currently, the optimal all-enzymatic process necessitates sequential in vitro transcription and capping reactions. This two-step requirement has hindered widespread implementation of an otherwise economical and environmentally sustainable capping solution in manufacturing processes. We hypothesized that this limitation could be overcome by fusion of a capping enzyme to the RNA polymerase to promote co-transcriptional capping through proximity to nascent transcripts. To achieve this, we selected the single-subunit capping enzyme from Faustovirus to fuse to the N-terminus of T7 RNA Polymerase via a short linker (CoZyCap T7 RNAP). Here we demonstrate that this novel fusion achieves high levels of 5’ capping co-transcriptionally with comparable RNA yield to the individual enzymatic reactions.