A bstract We consider higher-dimensional effective (EFT) operators consisting of fermion dark matter (DM) connecting to Standard Model (SM) leptons upto dimension six. Considering all operators together and assuming the DM to undergo thermal freeze-out, we find out relic density allowed parameter space in terms of DM mass ( m χ ) and New Physics (NP) scale (Λ) with one loop direct search constraints from XENON1T experiment. Allowed parameter space of the model is probed at the proposed International Linear Collider (ILC) via monophoton signal for both Dirac and Majorana cases, limited by the centre-of-mass energy $$ \sqrt{s} $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msqrt> <mml:mi>s</mml:mi> </mml:msqrt> </mml:math> =1 TeV, where DM mass can be probed within $$ {m}_{\chi }&lt;\frac{\sqrt{s}}{2} $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mi>m</mml:mi> <mml:mi>χ</mml:mi> </mml:msub> <mml:mo>&lt;</mml:mo> <mml:mfrac> <mml:msqrt> <mml:mi>s</mml:mi> </mml:msqrt> <mml:mn>2</mml:mn> </mml:mfrac> </mml:math> for the pair production to occur and Λ &gt; $$ \sqrt{s} $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msqrt> <mml:mi>s</mml:mi> </mml:msqrt> </mml:math> for the validity of EFT framework.