diff --git a/src/client/opamArg.ml b/src/client/opamArg.ml
index 5011db1a015..439622a4c0b 100644
--- a/src/client/opamArg.ml
+++ b/src/client/opamArg.ml
@@ -53,7 +53,9 @@ let preinit_environment_variables =
       "DEBUG", (fun v -> DEBUG (env_int v)),
       "see options `--debug' and `--debug-level'.";
       "YES", (fun v -> YES (env_bool v)),
-      "see option `--yes' and `--confirm-level`.";
+      "see option `--yes' and `--confirm-level`.
+       Priorities on confirmation environment variables: \
+       $(b,OPAMCONFIRMLEVEL), $(b,OPAMYES), $(b,OPAMNO)";
     ] in
   let client =
     let open OpamClientConfig.E in [
@@ -89,7 +91,9 @@ let environment_variables =
       "when set to $(i,always) or $(i,never), sets a default value for the \
        `--color' option.";
       "CONFIRMLEVEL", cli_from cli2_1, (fun v -> CONFIRMLEVEL (env_answer v)),
-      "see option `--confirm-level`.";
+      "see option `--confirm-level`.\
+       Priorities on confirmation environment variables: \
+       $(b,OPAMCONFIRMLEVEL), $(b,OPAMYES), $(b,OPAMNO)";
       "DEBUGSECTIONS", cli_from cli2_1, (fun v -> DEBUGSECTIONS (env_sections v)),
       "if set, limits debug messages to the space-separated list of \
        sections. Sections can optionally have a specific debug level (for \
@@ -108,8 +112,9 @@ let environment_variables =
       "MERGEOUT", cli_original, (fun v -> MERGEOUT (env_bool v)),
       "merge process outputs, stderr on stdout.";
       "NO", cli_original, (fun v -> NO (env_bool v)),
-      "answer no to any question asked, \
-       see option `--no` and `--confirm-level`.";
+      "answer no to any question asked, see option `--no` and `--confirm-level`.
+       Priorities on confirmation environment variables: \
+       $(b,OPAMCONFIRMLEVEL), $(b,OPAMYES), $(b,OPAMNO)";
       "PRECISETRACKING", cli_original, (fun v -> PRECISETRACKING (env_bool v)),
       "fine grain tracking of directories.";
       "SAFE", cli_original, (fun v -> SAFE (env_bool v)),
@@ -1140,17 +1145,22 @@ let global_options cli =
     mk_vflag_all ~cli [
       cli_original, true, ["y";"yes"],
       "Answer yes to all opam yes/no questions without prompting. \
+       See also $(b,--confirm-level). \
        This is equivalent to setting $(b,\\$OPAMYES) to \"true\".";
       cli_from cli2_1, false, ["no"],
       "Answer no to all opam yes/no questions without prompting. \
+       See also $(b,--confirm-level). \
        This is equivalent to setting $(b,\\$OPAMNO) to \"true\".";
     ]
   in
   let confirm_level =
     mk_enum_opt_all ~cli (cli_from cli2_1) ~section ["confirm-level"] "LEVEL"
       confirm_enum
-      (Printf.sprintf "Confirmation level, $(docv) must be %s. This is \
-                       equivalent to setting $(b, \\$OPAMCONFIRMLEVEL)`."
+      (Printf.sprintf
+         "Confirmation level, $(docv) must be %s. Can be specified more than \
+          once. If $(b,--yes) or $(b,--no) are also given, the value of the \
+          last $(b,--confirm-level) is taken into account. This is equivalent \
+          to setting $(b, \\$OPAMCONFIRMLEVEL)`."
          (string_of_enum confirm_enum))
   in
   let strict =
diff --git a/src/core/opamCoreConfig.ml b/src/core/opamCoreConfig.ml
index cf780aacf34..f0ba77dc54c 100644
--- a/src/core/opamCoreConfig.ml
+++ b/src/core/opamCoreConfig.ml
@@ -160,6 +160,7 @@ let initk k =
         | false -> None)
     ) in
   let answer =
+    (* priorities: confirm level > yes > no *)
     match E.confirmlevel (), E.yes (), E.no () with
     | Some c, _,  _ -> Some c
     | _, Some true, _ -> Some `all_yes