A bstract A measurement of the CP -violating parameters in $$ {B}_s^0\boldsymbol{\to}{D}_s^{\mp }{K}^{\pm} $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msubsup> <mml:mi>B</mml:mi> <mml:mi>s</mml:mi> <mml:mn>0</mml:mn> </mml:msubsup> <mml:mo>→</mml:mo> <mml:msubsup> <mml:mi>D</mml:mi> <mml:mi>s</mml:mi> <mml:mo>∓</mml:mo> </mml:msubsup> <mml:msup> <mml:mi>K</mml:mi> <mml:mo>±</mml:mo> </mml:msup> </mml:math> decays is reported, based on the analysis of proton-proton collision data collected by the LHCb experiment corresponding to an integrated luminosity of 6 fb − 1 at a centre-of-mass energy of 13 TeV. The measured parameters are obtained with a decay-time dependent analysis yielding C f = 0.791 ± 0.061 ± 0.022, $$ {A}_f^{\Delta \Gamma} $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msubsup> <mml:mi>A</mml:mi> <mml:mi>f</mml:mi> <mml:mrow> <mml:mtext>∆</mml:mtext> <mml:mi>Γ</mml:mi> </mml:mrow> </mml:msubsup> </mml:math> = −0.051 ± 0.134 ± 0.058, $$ {A}_{\overline{f}}^{\Delta \Gamma} $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msubsup> <mml:mi>A</mml:mi> <mml:mover> <mml:mi>f</mml:mi> <mml:mo>¯</mml:mo> </mml:mover> <mml:mrow> <mml:mtext>∆</mml:mtext> <mml:mi>Γ</mml:mi> </mml:mrow> </mml:msubsup> </mml:math> = −0.303 ± 0.125 ± 0.055, S f = −0.571 ± 0.084 ± 0.023 and $$ {S}_{\overline{f}} $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mi>S</mml:mi> <mml:mover> <mml:mi>f</mml:mi> <mml:mo>¯</mml:mo> </mml:mover> </mml:msub> </mml:math> = −0.503 ± 0.084 ± 0.025, where the first uncertainty is statistical and the second systematic. This corresponds to CP violation in the interference between mixing and decay of about 8.6 σ . Together with the value of the $$ {B}_s^0 $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msubsup> <mml:mi>B</mml:mi> <mml:mi>s</mml:mi> <mml:mn>0</mml:mn> </mml:msubsup> </mml:math> mixing phase −2 β s , these parameters are used to obtain a measurement of the CKM angle γ equal to (74 ± 12)° modulo 180°, where the uncertainty contains both statistical and systematic contributions. This result is combined with the previous LHCb measurement in this channel using 3 fb − 1 resulting in a determination of $$ \gamma ={\left({81}_{-11}^{+12}\right)}^{\circ } $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>γ</mml:mi> <mml:mo>=</mml:mo> <mml:msup> <mml:mfenced> <mml:msubsup> <mml:mn>81</mml:mn> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>11</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>12</mml:mn> </mml:mrow> </mml:msubsup> </mml:mfenced> <mml:mo>∘</mml:mo> </mml:msup> </mml:math> .