High entropy alloys thin films (HEA-TFs) have gained attention due to their interesting combination of properties such as high hardness and thermal stability while offering a wide range of chemical compositions, with potential applications for microscale electrical devices or high-performance coatings [1]. However, a nanoengineering approach based on the synthesis of new film architectures with controllable nanoscale features (i.e. grain size, nanolaminate structures) to improve mechanical properties is still an open challenge, requiring the implementation of novel deposition techniques in combination with post-thermal annealing treatments. Here, nanocrystalline CoCrCuFeNi HEA-TFs with a wide range of microstructures have been deposited using pulsed laser deposition (PLD) and magnetron sputtering. By controlling the background pressure in PLD, a transition from compact to nanogranular morphology was observed for deposition pressures >1 Pa, leading to a decrease in density and grain size (6.81 g/cm3 and 11 nm, respectively) compared to the compact counterpart (7.72 g/cm3 and 40 nm, respectively). Both compact and nanogranular films by PLD show increased hardness (≈10.5 GPa) compared to sputter-deposited films (≈8.3 GPa) due to their smaller grain size. Post-thermal annealing treatments reveal grain coarsening (up to 60 nm at 460°C) and segregation of a secondary BCC phase starting at 400°C for both compact and nanogranular films. However, nanogranular films maintain a lower grain size during annealing (< 20nm), thus retaining higher hardness of 8.5 GPa (Hall-Petch strengthening). In a second part, we will focus on Al/HEA nanolaminates by PLD and magnetron sputtering with bilayer period (Λ) ranging from 200 nm down to 2.5 nm, aiming to block the propagation of dislocations by controlling the interface density to improve hardness and yield strength [2]. Nanolaminates with different atomic compositions have been fabricated involving semi-coherent (FCC/FCC Al/CoCrCuFeNi) and incoherent (FCC/BCC Al/Al25(CoCrCuFeNi)75) interfaces to further hinder cross-layer dislocation propagation and boost mechanical properties. Among the main results, in situ micropillar compression test shows that incoherent interfaces have greater capability to improve yield strength (up to 2.5 GPa), while still showing great plastic deformability with no appearance of cracks even at 30% deformation. Our results show how PLD and sputtering can be used to control the nano-engineering of TF-HEAs, resulting in improved and tunable mechanical properties with key implications for industry applications. [1] N. I. M. Nadzri et al., ‘High-Entropy Alloy for Thin Film Application: A Review’, Coatings, 12, 2022 [2] A. Sàenz-Trevizo et al., Nanomaterials by design: a review of nanoscale metallic multilayers Nanotechnology, 31, 2020