linear spaces by virtue of its rich connection with several geometric properties of the space, like strict convexity, smoothness etc. [@J; @Ja; @Jb]. Recently, a renewed interest has been generated towards studying the Birkhoff-James orthogonality of elements in the space of bounded linear operators between normed linear spaces [@BS; @PSG; @SP]. While complete characterization of Birkhoff-James orthogonality of bounded linear operators defined on a Hilbert space [@BS; @P], or a finite dimensional real Banach space [@S] has been obtained, the problem of characterizing Birkhoff-James orthogonality of bounded linear operators on infinite dimensional normed linear spaces remains unsolved. Our present paper settles the issue in that direction. Also a complete characterization of the smoothness of bounded linear operators on infinite dimensional normed linear spaces remains elusive for long despite having been studied by many mathematicians like [@A; @DK; @HR; @HF; @HO; @KY; @R] over the years. Recently in [@PSG], a sufficient condition for the smoothness of a bounded linear operator has been obtained using Birkhoff-James orthogonality techniques. We carry on this work and prove separate necessary and sufficient conditions for smoothness of bounded linear operators on infinite dimensional normed linear spaces for the first time. Without further ado, let us establish 