A late crash had disrupted the flow of the peloton going into the finale of the flat stage from Camaiore to Follonica, but Kittel's Katusha-Alpecin team-mates managed to reassemble a compact lead-out for the German, who duly finished off their effort.
World champion Peter Sagan (Bora-Hansgrohe) placed second in the chaotic sprint, with Giacomo Nizzolo (Trek-Segafredo) in third.
Patrick Bevin's fifth place on the stage meant that he took over from BMC Racing team-mate Damiano Caruso at the top of the general classification. Caruso slips to second behind the New Zealander, with fellow BMC rider Greg Van Avermaet in third. BMC's dominance at the top of the GC came after the opening day's team time trial victory.
Adam Yates (Mitchelton-Scott) was one of those who was caught up in the crash with seven kilometres to go, and dropped out of the top 10 overall. Team Sky's Geraint Thomas and Chris Froome both move up overall, into seventh and ninth overall.
How it happened
The day's escape group of Nicola Bagioli (Nippo-Vini Fantini), Alexander Foliforov (Gazprom-Rusvelo), Jacopo Mosca (Wilier Triestina-Selle Italia) and Guy Sagiv (Israel Cycling Academy) formed on the early climb of Montemagno.
The quartet quickly opened up a decent gap over the BMC-controlled peloton, stretching it out to over five minutes after 20 kilometres.
Bagnoli appeared to be only interested in the mountain points on offer on the climb, and sat up 40km into the stage after cresting the climb first to leave just three out front.
The escape continued to work well together, and their advantage had been pushed out to over seven minutes inside 100km to go.
However, that was about to change as Mitchelton-Scott put Luke Durbridge on the front of the bunch. The Australian upped the pace considerably, and the gap started to reduce. He took several turns on the front over the rest of the stage and each time chipped more time away from the break.
Inside the final 50km, the gap was down to two minutes.
BMC took more of a back seat, allowing Mitchelton-Scott to continue working on the front with members of Quick-Step Floors, Trek-Segafredo and Katusha – all working for their sprinters.
The break's day out came to an end with 12km to go, which signalled a change in the composure of the bunch as riders started jostling for position on narrow roads with plenty of roundabouts, street furniture and corners.
A big crash took down a swathe of the peloton with 7km to go, as riders were spread all across the road.
The crash had disrupted some of the sprinters teams, and there was a lot of jostling and some elbows touching as lead-out trains tried to reassemble into the final 5km.
At one point it looked as though Katusha-Alpecin had formed two lead-outs, one on each side of the peloton as they tried to find Kittel. But find him they did, and the German looked to be back on top form as he opened up his sprint early after a final effort from team-mate Rick Zabel, and smoothly opened up a gap over his rivals.
Tirreno-Adriatico 2018 continues on Friday with stage three, from Follonica to Trevi and covering 234 kilometres. It promises to be a tough stage: not only the longest of the race, but peppered with climbs including the final, punchy ascent to the finish.
Tirreno-Adriatico 2018, stage two: Camaiore to Follonica, 167km
1. Marcel Kittel (Ger) Katusha-Alpecin
2. Peter Sagan (Svk) Bora-Hansgrohe
3. Giacomo Nizzolo (Ita) Trek-Segafredo
4. Michal Kwiatkowski (Pol) Team Sky
5. Patrick Bevin (NZl) BMC Racing
6. Jakub Mareczko (Ita) Wilier Triestina-Selle Italia
7. Fernando Gaviria (Col) Quick-Step Floors
8. Danny van Poppel (Ned) LottoNL-Jumbo
9. Eduard Micheal Grosu (Ven) Nippo Vini Fantini
10. Simone Consonni (Ita) UAE Team Emirates, all at same time
General classification after stage two
1. Patrick Bevin (NZl) BMC Racing, in 4-34-43
2. Damiano Caruso (Ita) BMC Racing, at same time
3. Greg Van Avermaet (Bel) BMC Racing, at same time
4. Rohan Dennis (Aus) BMC Racing, at same time
5. Daryl Impey (RSA) Mitchelton-Scott, at 4 secs
6. Michal Kwiatkowski (Pol) Team Sky, at 9 secs
7. Geraint Thomas (GBr) Team Sky, at 9 secs
8. Salvatore Puccio (Ita) Team Sky, at 9 secs
9. Chris Froome (GBr) Team Sky, at 9 secs
10. Jonathan Castroviejo (Spa) Team Sky, at 9 secs
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