Date: 201512
Local time of day: 0001-0600
Location: ZZZ.ARTCC, US
Flight conditions: VMC
Light: Daylight
Aircraft: B737 Undifferentiated or Other Model
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Cruise
Airspace: Class A ZZZ
ATC / advisory: Center ZZZ
Reporter organization: Air Carrier
Reporter function: Pilot Not Flying; Captain
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Second reporter function: First Officer; Pilot Flying
Anomaly: Flight Deck / Cabin / Aircraft Event Smoke / Fire / Fumes / Odor
Detector: Person Flight Attendant
When detected: In-flight
Result: Flight Crew Diverted; Flight Crew Landed As Precaution
Contributing factors: Aircraft
Primary problem: Aircraft

Narrative: Leveling at cruise; the First Officer (FO) flying; I was about to turn the seatbelt sign off after switching over to a new ZZZ Center frequency and he said the ride was smooth. I looked out the window and saw ZZZ right under us and that it was a clear and a nice day there. The Flight Attendant called up and asked if we smelled a burning smell. I looked at the FO and he said no. I did not either. I relayed that information to her and started to reach for the checklist and told her to keep me informed. About 30 seconds later she called again; and about that time both the First Officer and I started to smell a distinct faint odor that was not necessarily a smoke smell but a smell similar if the heat was turned up in the packs. I answered; and she said it was strong in the forward to mid part of the cabin around row seven to nine. With that; I told her that we were beginning to smell it also. I decided very quickly that I would rather put this aircraft on the ground rather than trouble shoot as we headed closer to the Gulf of Mexico and our options for landing became fewer. I told her that we were diverting to ZZZ and that I was going to start the checklist and would be back with her shortly. I immediately [advised] ZZZ Center and requested to divert to ZZZ and we needed lower. I knew we had plenty of fuel for the divert and that the weather was clear at ZZZ. The First Officer continued flying and talked to ATC; and I ran the checklist and coordinated with the Flight Attendants. We were cleared to 240 and a turn to the south. I looked at the pressurization panel to check on the gasper fan and it was already off. I started the checklist; and by the time I reached step 10; I called back to the Flight Attendant to ask how the situation was in the cabin. She said the smell had decreased in intensity. The smell in the cockpit was normal now and no hint of odor. She asked if they should clean up and take their seats. I said yes; and that I would check back in a few minutes. I used the ACARS to communicate with Dispatch to relay that we had a strong odor in the cabin and we were already diverting to ZZZ. The First Officer was doing a great job of flying and working the radios. We were given lower and I told him to hustle on down to 10;000 feet our clearance limit. I reached a stopping point in the checklist. The smell had dissipated to not there at all for us in the cockpit; and I focused my attention to help the First Officer fly and get set up for ZZZ.I called ZZZ Operations and let them know our situation and that we would be on the ground shortly. We were in still pretty tight to the airport and needed more altitude to lose and Approach gave a box pattern to the south to lose the altitude. I called again to the Flight Attendants and asked how they were; and that we would be on the ground in about five minutes. They said the smell had definitely dissipated. I said good and that I would make a brief PA to the Passengers. I made a PA to the folks that we had an odor in the cabin; and that out of caution we were landing in ZZZ and the aircraft is flying normal and we will have them on the ground shortly. By this time Approach was giving us lower and direct to ZZZZZ Intersection on the approach to Runway 4 for ZZZ. We had a few extra minutes and I reread the checklist quickly with the First Officer to double-check ourselves because we were very busy earlier in the flight. We landed and exited the runway with no issues. Operations told us that Gate XX was ours. After having Fire and Rescue check the outside of the aircraft; we proceeded to the gate. After the Passengers had deplaned; Fire and Rescue Personnel walked through the aircraft with a heat signal gun to double-check and found nothing. I called Dispatch and the Chief Pilot on Call after all the Passengers had exited and gave them my recount of the events.I felt like we handled the situation very well as a Crew. I thought we had good communication between allCrew Members. Having remembered previous aircraft incidents with any kind of smoke or fire caused me to maybe rush the checklist and make a decision probably faster than I would have liked. Having the station frequency removed from the Jepps program caused me to take additional time away from the task at hand to find it in myMobile365 since ZZZ was not on our trip that day. I would like to have that one piece of information back on the Jepps program.


Second narrative: [Report narrative contained no additional information.]


Synopsis: B737 flight crew reported deviating to an alternate after a Flight Attendant reported a smoky smell in the cabin.