Theoretical investigations on the encapsulation of atoms and molecules into carbon nanotubes (CNTs) are dominated primarily by first-principles calculations, molecular dynamics and Monte Carlo simulations. Herein, we model the encapsulation of helium clusters, Hen (n = 2–10) into CNTs by employing the continuum approximation in conjunction with the particle swarm optimization technique implemented with the well-known local search strategy, limited memory Broyden-Fletcher-Goldfarb-Shanno algorithm. The endohedral as well as exohedral binding of the noble gas atoms in the vicinity of CNTs is driven by weak van der Waals interactions. The analysis enabled us to predict the equilibrium geometries of the clusters under confinement as well as the optimal CNT radii for the encapsulation of the clusters. We probed the effect of length of the CNTs in governing the energetics of encapsulation by considering semi-infinite CNTs and nanotubes of finite lengths (L = 10 Å, 20 Å, and 30 Å). The putative global minima structures obtained from our analysis can be employed as initial guesses for electronic structure calculations.