Embodiments of a catheter insertion device are discussed comprising: an approximately hollow cylindrical catheter sleeve, at whose distal end a catheter is attached; a needle sleeve with a hollow needle, which is attached thereto and which, when ready for use, extends through the catheter sleeve and the catheter, and; a needle protective element that is arranged inside the catheter sleeve while being able to move on the needle. Said needle protective element has an engaging section that engages with an engaging device, which is formed in the vicinity of the needle tip, when the hollow needle is withdrawn from the catheter sleeve. A check valve is placed inside the catheter sleeve between the catheter and the needle protective element. The hollow needle, when ready for use, extends through said check valve, and the check valve automatically closes once the needle is withdrawn.