Police were at called at 02.47am on Thursday, 30 July to reports of a stabbing at Clements Court on Green Lane in Hounslow.
Officers and the London Ambulance Service attended. At the scene a 32-year-old man was found suffering from stab wounds.
Despite the efforts of medics at the scene, he was pronounced dead at 3.45am. His next of kin have been informed.
A post-mortem examination will be scheduled in due course.
A 22-year-old woman was arrested on suspicion of conspiracy to murder. She was taken to a central London police station where she remains at this time.
A murder investigation has been launched led by Detective Chief Inspector Rob Pack, who said: “At this early stage we are retaining an open mind concerning motive, and are keen to hear from anyone who has information or footage of the events leading up to the attack that ended this man’s life.
“There was a party going on at the venue; there were lots of people there and I urge those people to come forward and pass on what they saw – no matter how insignificant it may seem.
“In addition, anyone who was in the area during the early hours of Thursday morning and noticed anything unusual or suspicions should contact my team without delay.”
Local policing commander Chief Superintendent Peter Gardner, said: “This is a senseless act of violence and we have needlessly lost another life at the point of blade. My thoughts and condolences are with the victim’s family at this desperately sad time. I’d like to thank the officers and members of the London Ambulance Service that were first on the scene and worked tirelessly to try and save the life of the victim.
“We understand the impact of violent crime on our communities and residents can expect to see an increased police presence in the area as part of reassurance patrols. There will be some disruption to the local area whilst crime scenes are in place as part of our investigation. Please do speak with officers about any concerns you may have, or information that you would like to provide.”
Anyone with information asked to call 101 or Tweet @MetCC quoting reference Cad 843/30Jul.