Electronic Journal of Differential Equations, Vol. 2019 (2019), No. 106, pp. 1-26. Title: Lagrangian structure for compressible flow in the half-space with Navier boundary condition Authors: Marcelo M. Santos (Univ. Estadual de Campinas, SP, Brazil) Edson J. Teixeira (Univ. Federal de Vicosa, MG, Brazil) Abstract: We show the uniqueness of particle paths of a velocity field, which solves the compressible isentropic Navier-Stokes equations in the half-space $\mathbb{R}_+^3$ with the Navier boundary condition. More precisely, by energy estimates and the assumption of small energy we prove that the velocity field satisfies regularity estimates which imply the uniqueness of particle paths. Submitted March 5, 2019. Published September 18, 2019. Math Subject Classifications: 35Q30, 76N10, 35Q35, 35B99. Key Words: Navier-Stokes equations; Lagrangian structure; Navier boundary condition.