A reagent vessel holder for an analytical instrument is disclosed. The reagent vessel holder comprises at least one reagent vessel compartment for receiving a reagent vessel, wherein the reagent vessel compartment comprises a base and at least two lateral guiding elements, and at least one hollow needle for piercing the reagent vessel. The hollow needle is disposed on a front end of the reagent vessel compartment near the base and extends in a direction substantially parallel to the base. The lateral guiding elements are disposed so as to be adapted to slidably guide the reagent vessel in a direction substantially parallel to the direction, in which the hollow needle extends. The lateral guiding elements are adapted to receive the reagent vessel therebetween and are biased towards one another. Further, a reagent supply system for an analytical instrument and an analytical instrument comprising such a reagent vessel holder are disclosed.