A bstract The difference between the CP asymmetries in the decays Λ c + → pK − K + and Λ c + → pπ − π + is presented. Proton-proton collision data taken at centre-of-mass energies of 7 and 8 TeV collected by the LHCb detector in 2011 and 2012 are used, corresponding to an integrated luminosity of 3 fb −1 . The Λ c + candidates are reconstructed as part of the Λ b 0 → Λ c + μ − X decay chain. In order to maximize the cancellation of production and detection asymmetries in the difference, the final-state kinematic distributions of the two samples are aligned by applying phase-space-dependent weights to the Λ c + → pπ − π + sample. This alters the definition of the integrated CP asymmetry to A CP wgt ( pπ − π + ). Both samples are corrected for reconstruction and selection efficiencies across the five-dimensional Λ c + decay phase space. The difference in CP asymmetries is found to be $$ \begin{array}{c}\hfill \Delta {A}_{CP}^{\mathrm{wgt}}={A}_{CP}\left(p{K}^{-}{K}^{+}\right) - {A}_{CP}^{\mathrm{wgt}}\left(p{\pi}^{-}{\pi}^{+}\right)\hfill \\ {}\hfill = \left(0.30 \pm 0.91 \pm 0.61\right)\ \%,\hfill \end{array} $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mtable> <mml:mtr> <mml:mtd> <mml:mi>Δ</mml:mi> <mml:msubsup> <mml:mi>A</mml:mi> <mml:mrow> <mml:mi>C</mml:mi> <mml:mi>P</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>w</mml:mi> <mml:mi>g</mml:mi> <mml:mi>t</mml:mi> </mml:mrow> </mml:msubsup> <mml:mo>=</mml:mo> <mml:msub> <mml:mi>A</mml:mi> <mml:mrow> <mml:mi>C</mml:mi> <mml:mi>P</mml:mi> </mml:mrow> </mml:msub> <mml:mfenced> <mml:mrow> <mml:mi>p</mml:mi> <mml:msup> <mml:mi>K</mml:mi> <mml:mo>−</mml:mo> </mml:msup> <mml:msup> <mml:mi>K</mml:mi> <mml:mo>+</mml:mo> </mml:msup> </mml:mrow> </mml:mfenced> <mml:mspace /> <mml:mo>−</mml:mo> <mml:msubsup> <mml:mi>A</mml:mi> <mml:mrow> <mml:mi>C</mml:mi> <mml:mi>P</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>w</mml:mi> <mml:mi>g</mml:mi> <mml:mi>t</mml:mi> </mml:mrow> </mml:msubsup> <mml:mfenced> <mml:mrow> <mml:mi>p</mml:mi> <mml:msup> <mml:mi>π</mml:mi> <mml:mo>−</mml:mo> </mml:msup> <mml:msup> <mml:mi>π</mml:mi> <mml:mo>+</mml:mo> </mml:msup> </mml:mrow> </mml:mfenced> </mml:mtd> </mml:mtr> <mml:mtr> <mml:mtd> <mml:mo>=</mml:mo> <mml:mspace /> <mml:mfenced> <mml:mrow> <mml:mn>0.30</mml:mn> <mml:mspace /> <mml:mo>±</mml:mo> <mml:mspace /> <mml:mn>0.91</mml:mn> <mml:mspace /> <mml:mo>±</mml:mo> <mml:mspace /> <mml:mn>0.61</mml:mn> </mml:mrow> </mml:mfenced> <mml:mspace /> <mml:mo>%</mml:mo> <mml:mtext>,</mml:mtext> </mml:mtd> </mml:mtr> </mml:mtable> </mml:math> where the first uncertainty is statistical and the second is systematic.