A blow-by gas filtration assembly fluidically connectable to the crankcase ventilation circuit of an internal combustion engine to receive blow-by gases and filter them from the suspended particles contained therein, wherein the filtration assembly has an axis (X-X) and comprises: - a main body comprising a filtration chamber extending along said axis (X-X) and an outlet mouth made at the axis (X-X); - a filter group which extends along the axis (X-X) and has a hollow cylindrical shape comprising a central cavity, housed in said filtration chamber crossable by blow-by gases radially from the outside to the inside; - a command group supported on the main body operatively connected to the filter group to command it in rotation about the axis (X-X); - a support group supporting the filter group to the main body, comprising: i) a bearing element comprising an outer fifth wheel sealingly engaging an outlet edge defining the outlet mouth and an inner fifth wheel defining an outlet passage through which filtered blow-by gases flow; ii) a hollow tubular member extending along the axis (X-X), defining an outlet duct of the filtered blow-by gases, comprising a bearing end operatively connected to the inner fifth wheel and a support portion extending from said bearing end, in the central cavity, so that the filter assembly is mounted on said support portion and fluidly communicates with the outlet mouth; wherein the bearing element and the hollow tubular element are reciprocally sealingly joined; wherein the blow-by gas filtration assembly is characterized in that the bearing end comprises an inner annular section, preferably proximal to the support portion, which sealingly annularly engages the inner fifth wheel. - a main body comprising a filtration chamber extending along said axis (X-X) and an outlet mouth made at the axis (X-X); - a filter group which extends along the axis (X-X) and has a hollow cylindrical shape comprising a central cavity, housed in said filtration chamber crossable by blow-by gases radially from the outside to the inside; - a command group supported on the main body operatively connected to the filter group to command it in rotation about the axis (X-X); - a support group supporting the filter group to the main body, comprising: i) a bearing element comprising an outer fifth wheel sealingly engaging an outlet edge defining the outlet mouth and an inner fifth wheel defining an outlet passage through which filtered blow-by gases flow; ii) a hollow tubular member extending along the axis (X-X), defining an outlet duct of the filtered blow-by gases, comprising a bearing end operatively connected to the inner fifth wheel and a support portion extending from said bearing end, in the central cavity, so that the filter assembly is mounted on said support portion and fluidly communicates with the outlet mouth; wherein the bearing element and the hollow tubular element are reciprocally sealingly joined; wherein the blow-by gas filtration assembly is characterized in that the bearing end comprises an inner annular section, preferably proximal to the support portion, which sealingly annularly engages the inner fifth wheel. i) a bearing element comprising an outer fifth wheel sealingly engaging an outlet edge defining the outlet mouth and an inner fifth wheel defining an outlet passage through which filtered blow-by gases flow; ii) a hollow tubular member extending along the axis (X-X), defining an outlet duct of the filtered blow-by gases, comprising a bearing end operatively connected to the inner fifth wheel and a support portion extending from said bearing end, in the central cavity, so that the filter assembly is mounted on said support portion and fluidly communicates with the outlet mouth; wherein the bearing element and the hollow tubular element are reciprocally sealingly joined; wherein the blow-by gas filtration assembly is characterized in that the bearing end comprises an inner annular section, preferably proximal to the support portion, which sealingly annularly engages the inner fifth wheel.