Brunei Darussalam, China (mainland), Indonesia, Japan, Malaysia, Philippines, Russia (Asian), South Korea, Taiwan (China), USA.
Vagrant to Hong Kong (China).
Breeds eastern Russia (coast of Sea of Okhotsk from Magadan south to mouth of R Amur, also Kamchatka), Sakhalin I, Kuril Is and northern Japan (northern & eastern Hokkaido); non-breeding Philippines and northern Borneo.
 
Population
Estimated population is unknown (2010).
Middendorff's Grasshopper Warbler (Helopsaltes ochotensis) [XC178145]
by Malte Seehausen from Notsuke Peninsula, Notsuke-gun, Hokkaido Prefecture, Russian Federation (song)
Middendorff's Grasshopper Warbler (Helopsaltes ochotensis) [XC286295]
by Vadim Ivushkin from Kiritappu area, Hokkaido, Japan (song)
Nest
Composed of dead leaves, plant stems and dried grass, lined with plant fiber and other fine materials, in grass or reeds on the ground.
Eggs (Guide)
5 - 6; pink with black streaks. Incubation: about 13 - 15 days; by female.
Subspecies
Forms a superspecies with Pallas's Warbler (Locustella certhiola) and Pleske's Warbler (Locustella pleskei). Has been considered conspecific with one or both.
Proposed subspecies subcerthiola (Kamchatka and northern Kurils, non-breeding Philippines) considered indistinguishable from birds elsewhere in range.
The following 2 subspecies are recognised:
subcerthiola Swinhoe, 1874 - Kamchatka Peninsula and northern Kuril Islands. Winters to Philippines.
ochotensis (Middendorff, 1853) - Far eastern Russia and northern Japan.
The Field Guide to the Birds of Australia Pizzey, G., and Knight, E., 1997, Angus & Robertson, Sydney ISBN 0 207 19691 5
Field Guide to Australian Birds Morecombe, M., 2000, Steve Parish Publishing Pty Ltd. ISBN 1 876282 10 X
Field Guide to the Birds of Australia Simpson, K., and Day, N., 1999, 6th Edition, Viking ISBN 0 670 87918 5
Reader's Digest Complete Book of Australian Birds 1988, 2nd Edition, Reader's Digest ISBN 0 949819 99 9
What Bird is That? 1984, Revised Edition, Angus & Robertson, Sydney ISBN 0 207 14846 5
Handbook of Australian, New Zealand & Antarctic Birds 1990 - , Oxford University Press, Melbourne ISBN 0 19 553244 9