A fitting for connecting pipes, in particular at least a pipe of the pipes being flexible, comprising: - at least a first tubular element provided, at an end thereof, with a first inlet/outlet opening and defining internally 5 thereof a first conduit; - at least a second tubular element provided, at an end thereof, with a second inlet/outlet opening and defining internally thereof a second conduit, said first tubular element and second tubular element being connected with one another, at respective ends opposite to the respective inlet/outlet opening, such that said first conduit and second conduit are in communication with one another and overall define an assembly conduit, putting said first opening and said second opening in fluid communication, the fitting further comprising at least first blocking means comprising: - a sleeve associable to the first tubular element such as to surround the first tubular element externally and to create, between the sleeve and the first tubular element, an annular housing destined to insertingly receive a pipe, the pipe being interposed between the first tubular element and the sleeve, said sleeve having an internal surface, facing towards the first tubular element, and an external surface, and being provided with at least an annular protrusion extending from said external surface and with at least an annular gully afforded in said internal surface at said annular protrusion; - at least a blocking ring housable in said at least an annular gully of said sleeve; said first blocking means being configured for operating at least in an insertion configuration, in which they enable insertion of a pipe into said annular housing, and a blocked configuration, in which they stably and fluid-sealingly block the pipe in the annular housing, characterized in that the first tubular element comprises at least a first sealing element, externally enveloping the tubular element in such a way as to be interposed between the tubular element and a pipe inserted in said annular housing, said first sealing element being deformable, when the first blocking means are in the blocking configuration, such as to inhibit a fluid communication between the first conduit and an external surface of the first tubular element. - at least a first tubular element provided, at an end thereof, with a first inlet/outlet opening and defining internally 5 thereof a first conduit; - at least a second tubular element provided, at an end thereof, with a second inlet/outlet opening and defining internally thereof a second conduit, - a sleeve associable to the first tubular element such as to surround the first tubular element externally and to create, between the sleeve and the first tubular element, an annular housing destined to insertingly receive a pipe, the pipe being interposed between the first tubular element and the sleeve, said sleeve having an internal surface, facing towards the first tubular element, and an external surface, and being provided with at least an annular protrusion extending from said external surface and with at least an annular gully afforded in said internal surface at said annular protrusion; - at least a blocking ring housable in said at least an annular gully of said sleeve;