One man was taken to hospital after what officers suspect was an attack on Langdale Street at 3.45pm.
Police are trying to establish what happened.
A spokesperson for West Yorkshire Police said: "Police were called to reports of a public order incident on Langdale Street, Elland, shortly after 3.45pm yesterday.
"Upon arrival, one man was taken to hospital by ambulance following a suspected serious assault. His injuries are not believed to be life-threatening.
"Enquiries are ongoing to establish what happened.
"Anyone with information relating to the incident is asked to call Calderdale CID on 101, or go online at www.westyorkshire.police.uk/101livechat quoting reference 13220337997."