A compact and planar donor–acceptor molecule 1 comprising tetrathiafulvalene (TTF) and benzothiadiazole (BTD) units has been synthesised and experimentally characterised by structural, optical, and electrochemical methods. Solution‐processed and thermally evaporated thin films of 1 have also been explored as active materials in organic field‐effect transistors (OFETs). For these devices, hole field‐effect mobilities of μFE=(1.3±0.5)×10−3 and (2.7±0.4)×10−3 cm2 V s−1 were determined for the solution‐processed and thermally evaporated thin films, respectively. An intense intramolecular charge‐transfer (ICT) transition at around 495 nm dominates the optical absorption spectrum of the neutral dyad, which also shows a weak emission from its ICT state. The iodine‐induced oxidation of 1 leads to a partially oxidised crystalline charge‐transfer (CT) salt {(1)2I3}, and eventually also to a fully oxidised compound {1I3}⋅1/2I2. Single crystals of the former CT compound, exhibiting a highly symmetrical crystal structure, reveal a fairly good room temperature electrical conductivity of the order of 2 S cm−1. The one‐dimensional spin system bears compactly bonded BTD acceptors (spatial localisation of the LUMO) along its ridge. Compact donor–acceptor dyad: A compact and planar donor–acceptor molecule 1 comprising tetrathiafulvalene (TTF) and benzothiadiazole (BTD) units has been prepared for investigation of its photoinduced intramolecular charge‐transfer process. Chemical oxidation of 1 affords a partially oxidised crystalline charge‐transfer (CT) salt {(1)2I3}, and eventually also a fully oxidised compound {1I3}⋅1/2I2. The former CT salt exhibits a highly symmetrical crystal structure, forming a wire of TTF+0.5 π‐stacks with compactly bonded BTD acceptors along its ridge (see graphic). This unique structural feature accounts for its good electrical conductivity of 2 S cm−1 at room temperature.